A pretence of surprise at having jumped the gun? (5,5)
I believe the answer is:
false start
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for false start that I've seen before include "Unsuccessful beginning" , "In which runner is seen to have jumped the gun" , "may lead to total recall" , "In which someone jumps the gun" .)