Motherwell
On The Bench
He headed home Simon Lappin's cross to maintain the Fir Parkers' pursuit of third-placed Dundee United just when it seemed that the second-bottom Rugby Park side were about to collect a much-needed point.
Strike partner Ross McCormack had missed a first-half penalty, conceded by David Lilley, and the Kilmarnock defender was sent off for a second booking after fouling McCormack midway through the second half.
It was Motherwell's first game in 18 days, and Mark McGhee made two changes to the team which had secured Scottish Cup fourth-round victory over Hearts before the waterlogged Fir Park pitch forced four successive postponements and the relaying of a quarter of the surface.
Steven Hammell, who rejoined Motherwell from Southend on transfer deadline day, went straight in at left-back in place of Jim Paterson, who signed for Plymouth on the same day. Steven McGarry joined the forward line in place of Chris Porter, still recovering from a knee injury.
Kilmarnock also made two changes to the side which lost 5-1 at home to Celtic in last weekend's Scottish Cup fifth round. David Lilley and Paul Di Giacomo started in place of the benched Willie Gibson and Frazer Wright, who dropped out of the squad.
McGarry came close to an early opener after just two minutes when Clarkson turned past former colleague Martyn Corrigan on the left byline and played the ball back to Stephen Hughes, but McGarry turned his pass into the centre of the goal just wide of the near post.
Kilmarnock had an equally near miss on seven minutes when Lilley's header drifted past the right-hand post from Di Giacomo's corner on the opposite side. They then strung together a promising series of passes from which Corrigan blasted a long-range drive over the bar following Jamie Hammill's pass.
Motherwell sought a foul when Garry Hay hauled down Clarkson on the right edge of the box on 18 minutes but they were awarded a penalty four minutes later when Lilley flattened the striker as he raced through the left-hand side of the box.
The Kilmarnock defender escaped only with a booking for both the foul and his furious protests as he stood over the Motherwell player, in which he was joined by goalkeeper Alan Combe.
But the scoreline remained goalless as McCormack sent his spot kick inches wide of the left-hand post.
Marc Fitzpatrick was next to come close to the opening goal on 32 minutes when he latched on to a pass into the centre of the box from fellow midfielder Keith Lasley, but Danny Invincibile made a last-ditch tackle and the home player sent his shot from 10 yards off to the right of goal.
Clarkson then played a reverse pass to McCormack on the edge of the area and he teed up McGarry, but the striker's high looping effort took a deflection and was comfortably caught by Combe.
McGarry fired a speculative drive well wide of the right-hand post seven minutes from the break.
The second half was only three minutes old when Kilmarnock manager Jim Jefferies found himself on the receiving end of a lecture from referee Mike McCurry.
Stephen Craigan's long ball into the penalty box two minutes later took out the defence and presented Clarkson with a decent opportunity, but the striker failed to add sufficient power to his close-range chip and it landed softly in Combe's waiting arms.
McCormack was again inches away from the opener on 54 minutes.
Hammell ran up the left and played in a ball which McCormack intelligently left for Clarkson, who laid it back out to him on the left, only for the striker's diagonal shot to sneak wide of the far upright.
Motherwell's best chance to open the scoring came in 68 minutes when Hammell played a good ball across the box which landed at the feet of Lasley.
Instead of going for goal he played the ball back to McCormack and the Kilmarnock defenders threw themselves in the way as neither McCormack nor Hughes were able to bundle home.
Kilmarnock were reduced to 10 men when a Motherwell attack up the left was halted in its tracks by fouls seconds apart on Clarkson and McCormack by James Fowler and Lilley respectively.
Both visiting players were booked and Lilley, cautioned for conceding the earlier penalty, walked with 19 minutes remaining.
Home goalkeeper Graeme Smith did well to smother Simon Ford's attempt to turn home a Hay free-kick and, at the other end, Fitzpatrick bulleted a header past the post from Paul Quinn's cross.
The points looked certain to be shared after Hammell's 89th-minute free-kick from 25 yards was clawed out by Combe from the top left corner of his goal.
But Motherwell secured all three points two minutes into injury time when substitute Lappin crossed from the left and Clarkson headed home.
