Leicester (13) 20
Tries: Allen, Hamilton Cons: Flood 2 Pens: Flood 2
Clermont Auvergne (9) 15
Pens: James 2 Drop-goals: James 3
Allen's marvellous try set Leicester on their way to a gripping victory
Leicester kept their Heineken Cup Pool Three hopes alive with a narrow win but Clermont Auvergne secured what may prove to be a vital losing bonus point.
Two penalties from Toby Flood, to two Brock James drop-goals, made it 6-6.
Leicester scored a stunning converted try from Anthony Allen but a James penalty made it 13-9 at the break.
Scott Hamilton's try, superbly converted by Flood, put Leicester eight points clear but James's late penalty gave Clermont a precious bonus point.
The Tigers went into the game on the back of a battering away to Clermont last weekend, despite three late tries giving the scoreline a misleading gloss.
Having been outmuscled in the Massif Central and with their Heineken Cup hopes hanging by a thread they were determined not to be bullied in front of a packed Welford Road, and they duly turned in a hugely committed performance on a damp evening in the Midlands.
Leicester lost tight-head prop Martin Castrogiovanni to injury just six minutes into the game but took the lead soon after through a Flood penalty after a powerful surge from former Australia winger Lote Tuqiri.
But the visitors were soon level as France winger Julien Malzieu more than matched Tuqiri with a thunderous run into the heart of the Leicester defence to set up James for a simple drop-goal.
Flood quickly edged Leicester back into the lead with his second penalty but a second James drop-goal tied things up once again, only for the Tigers to take the lead with a dazzling try.
Clean ball off the top of a line-out gave Ben Youngs the chance to snipe through the back of the Clermont line-out and after handing off two tacklers the 20-year-old scrum-half tied Aurelien Rougerie in knots before popping a pass to Allen to crash over.
Flood converted but although James missed a long-range penalty for the visitors he was on target with a much shorter effort just before the break to trim Leicester's lead to four points.
The successful kick was not without controversy, as it took the Television Match Official to confirm it had successful bisected the posts, but the correct decision was arrived at eventually.
Leicester dominated territory and possession in the third quarter but, with Flood missing a penalty, could not add to their score.
Flood and Dan Hipkiss both made threatening breaks but Clermont held firm and they trimmed the gap to just one point when James popped over his third drop-goal to cap a rare raid into Leicester territory by the French side.
Leicester launched another series of desperate attacks but just when it looked like they would fail to add to their score, Clermont failed to deal with a speculative kick and former All Black Hamilton pounced.
The Leicester full-back seized on a loose ball and raced 50m to score in the corner, with Flood's superb touchline conversion briefly relieving Clermont of their losing bonus point.
But from the restart Lewis Moody was penalised for being off-side when the Tigers knocked the ball on, almost straight into his arms.
James kept his nerve to drill the ball between the posts and give Clermont a losing bonus point for finishing within seven points which may prove decisive in such a competitive pool.
Leicester coach Matt O'Connor:
"I am pleased with the win but not with the fact that they leave with a bonus point from a game we largely dominated.
"We didn't get the rub of the green with certain decisions, but the win keeps us in there fighting. I'm convinced one of us will go through as a successful runner-up, but it will go down to the wire.
"When Scott Hamilton scored his try, it was a relief all round and now we look forward to the last two rounds."
Clermont coach Vern Cotter:
"We knew, above all, we had to come away with something from this game - and we have.
"This is a famous European venue, and it was every bit as good an atmosphere as we expected.
"I am proud of the way we hit back fast after falling eight points behind minutes from time and out of the losing bonus point zone."
Leicester: Hamilton; Tuilagi, Hipkiss, Allen, Tuqiri; Flood, B Youngs; Ayerza, Davies, Castrogiovanni, L Deacon, Parling, Newby, Moody, Crane.
Replacements: J Murphy for Tuilagi (66), Staunton for Hipkiss (34), Chuter for Davies (66), Cole for Castrogiovanni (7).
Not Used: Stankovich, Kay, B. Deacon, Ellis.
Clermont Auvergne: Floch; Rougerie, Canale, Bai, J Malzieu; James, Parra, Faure, Ledesma, Zirakashvili, Cudmore, Pierre, Bonnaire, Audebert, Vermeulen.
Replacements: Fofana for Canale (70), Senio for Parra (66), Domingo for Faure (43), Scelzo for Zirakashvili (71), Privat for Cudmore (63), White for Vermeulen (51).
Not Used: Wepener, Russell.
Ref: Nigel Owens (WRFU).