Dispute a win, for example (7)
I believe the answer is:
gainsay
'dispute' is the definition.
(I know that dispute can be written as gainsay)
'a win for example' is the wordplay.
'a win' becomes 'gain' (I've seen this before).
'for example' becomes 'say' ('say' can be used to introduce an example).
'gain'+'say'='GAINSAY'
(Other definitions for gainsay that I've seen before include "Speak against" , "Challenge, dispute" , "Contradict, deny, dispute" .)