Fund defender to get revenge (7)
I believe the answer is:
payback
'revenge' is the definition.
(I've seen this before)
'fund defender' is the wordplay.
'fund' becomes 'pay'.
'defender' becomes 'back' (I've seen this before).
'pay'+'back'='PAYBACK'
'to get' acts as a link.
(Other definitions for payback that I've seen before include "act of revenge" , "Financial return" , "return on investment" , "Profit" .)