61 mins
David Silva was next to threaten for the visitors, curling a shot narrowly wide.
There was a lethargy about the Ibrox side's play, but they almost took the lead when Diouf's corner was knocked towards goal by Kyle Bartley and Mohamadou Sissoko was well placed to clear.
Diouf missed a gilt-edged chance, firing wide from six yards after Steven Davis's free-kick was diverted into his path.
Kilmarnock goalkeeper Anssi Jaakkola spared Manuel Pascali's blushes when he collected the ball after the defender's clearance spun towards his own goal.
Bartley headed Diouf's corner over and, at the other end, Hamill's shot spun wide of Allan McGregor's goal, the keeper restored to the Rangers line-up after being rested in midweek.
Rangers' play lacked creativity and their use of the ball was at times careless, but they took the lead in the 38th minute after breaking up a Kilmarnock advance.
Gros and Liam Kelly got in a muddle in the middle of the park and Rangers quickly moved the ball forward.
Steven Whittaker's pass found Diouf on the right-hand side and the on-loan Blackburn player fired home from inside the penalty area.
Nikica Jelavic forced Jaakkola into a save in the early stages of the second half when a pass to a team-mate may have been a better option for the Rangers striker.
Rangers
appeared to be happy to sit on their lead and were
punished when Killie were awarded a spot-kick.
Foster's high challenge on Clancy was penalised by referee Alan Muir and Hamill converted from 12 yards.
The hosts went in search of the lead again and Diouf's free-kick was volleyed over by Bartley.
Foster tried his luck from 25 yards, but the left-foot effort dropped over the crossbar and Davis's free-kick attempt was also too high.
Rangers had two penalty claims turned down, Jelavic going down under pressure from the visiting defence before the home fans claimed the ball had struck the arm of Killie's Garry Hay.
In between times, Kyle Lafferty and Weiss were sent on from the Rangers bench for the final 15 minutes, Diouf and Foster withdrawn, as manager Walter Smith looked for a fresh impetus.
Rui Miguel, who had come on for Gros, went to ground in the Rangers box under pressure from Bartley but referee Muir again waved play on.
Sissoko sustained an injury and left the field, but Kilmarnock had to wait until a break in play to send on a replacement.
And while they were down to 10 men, the Ayrshire side fell behind again as Weiss's cross into a dangerous area was knocked past Jaakkola by the unfortunate Clancy.
Kilmarnock went in search of a second equaliser and had further penalty appeals turned down after Lafferty collided with Clancy in the area.
Sandy's Match Pic's are HERE
