Rebound adversely (8)
I believe the answer is:
backfire
'rebound adversely' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for backfire that I've seen before include "Cause a result opposite to that intended" , "Rebound on oneself" , "report" , "Have the opposite and damaging effect to that intended" , "Have an unintended negative consequence" .)