Clare edged out Cork in Cusack Park to advance to the Munster Football Championship semi-finals and put a number of counties in jeopardy of missing out on the All-Ireland Football Championship.
The Rebels led by 0-06 to 0-04 at half-time, with just a single score from play by the visitors.
In front of 3,661 spectators, Stephen Sherlock extended the advtantage to four points.
He scored 10 of the 13 points in the game, but it was Clare who finished the stronger.
Kevin O'Donovan had looked to rescue extra-time for Cork, only for Cillian Rouine to win the game in the fourth minute of added-time.
The result has big implications elsewhere, with Meath now required to reach the Leinster final if they are to qualify for the Sam Maguire Cup race.
Clare face Limerick in the Munster semi-final, both having been relegated to Division 3 in the spring, with one of them destined to break into the Sam Maguire competition.
Cork must rely on their good league standing in order to be part of the round-robin series.
When Cork eased four points clear early in the second half of this slow-burning contest it looked as if they had taken the sting out of Clare's challenge and were on the road to a comfortable victory.
However, after leaking 0-03 inside as many minutes to trail by 0-9 to 0-5 after 40 minutes it was as if the stark prospect of being eliminated from the race for Sam Maguire on the first day out lit a fire in everyone of a saffron and blue hew.
From there they produced something special with a dominant closing 30 minutes carrying them to a first senior championship victory over Cork in 26 years, with the clinching score coming in the 75th minute when corner-back Rouine fisted the ball over from close range.
It was breathless stuff, just as it was inspired as Clare's fightback was started by captain Eoin Cleary’s 42nd minute point, with man-of-the-match Keelan Sexton and Emmet McMahon following with further points as Clare got back on terms at 0-09 apiece with 15 minutes remaining as a rip-roaring end-to-end contest developed.
This excitement was in stark contrast to a pedestrian first half in which Cork eked out a 0-06 to 0-04 lead thanks to the accuracy of free-taker Sherlock — he landed 0-05, with their only point from play via centre-back Rory Maguire in the 26th minute.
Clare had started well with a brace from full-forward Keelan Seton inside four minutes, but seven poor wides and ill-discipline in defence cost them dear. Points by captain Eoin Cleary and Podge Collins on 15 and 28 minutes respectively did stop the rot, but their half-time deficit would have been much greater if Brian O’Driscoll’s rasping drive had found the net instead of the crossbar in the 20th minute.
Ultimately, this let-off paved the way for Clare’s renaissance, as did the inspiration that flowed when it was needed most as an inspired Sexton, Gavin Cooney, Jamie Malone and Eoin Cleary came up with key scores down the stretch, while midfielder Darren O’Neill was immense.
Jamie Malone’s 61st minute effort edged the Banner 0-12 to 0-11 clear but with Sherlock bringing his total double figures it wasn’t until the last move of the match that started with keeper Stephen Ryan and was taken on by Ciaran Russell that Rouine decided matters for once and for all for a deserved win.
Clare: Stephen Ryan; Manus Doherty, Cillian Brennan, Cillian Rouine (0-01); Ciaran Russell, Jamie Malone (0-01), Daniel Walsh; Cathal O’Connor, Darragh Bohannon; Pearse Lillis, Emmet McMahon (0-02), Dermot Coughlan; Eoin Cleary (0-04, 2f)), Keelan Sexton (0-04), Padraic Collins (0-01).
Subs Darren O’Neill for Cathal O’Connor (Half-Time), Gavin Cooney (0-01) for Coughlan (50), Mark McInerney for McMahon (68), Alan Sweeney for Collins (72).
Cork: Micheál Aodh Martin; Kevin O’Donovan (0-01), Daniel O’Mahony, Tommy Walsh; Luke Fahy, Rory Maguire (0-01), Mattie Taylor; Colm O’Callaghan, Ian Maguire; Eoghan McSweeney, Sean Powter (0-01), Brian O’Driscoll; Ruairi Deane, Chris Óg Jones, Stephen Sherlock (0-10, 7f, 1 ’45).
Subs Killian O’Hanlon for McSweeney (48), Conor Corbett for Jones (57), John O’Rourke for O’Driscoll (68), Cian Kiely for Fahy (68).
Referee: Fergal Kelly (Longford)
