Collapse with strain during competition (5,2)
I believe the answer is:
crack up
'collapse' is the definition.
(I know that crack-up is a type of collapse)
'strain during competition' is the wordplay.
'strain' becomes 'rack' (racking is a kind of straining).
'during' means one lot of letters goes inside another.
'competition' becomes 'cup' (eg the FA Cup).
'rack' put into 'cup' is 'CRACK-UP'.
'with' is the link.
(Other definitions for crack up that I've seen before include "Have a nervous breakdown" , "laugh out loud?" , "Collapse under strain; praise" , "Fail" , "Laugh without restraint" .)