Defender put on boot for illicit payment
I believe the answer is:
kickback
'illicit payment' is the definition.
(I've seen this before)
'defender put on boot' is the wordplay.
'defender' becomes 'back' (I've seen this in other clues).
'put on' is a charade indicator (letters next to each other).
'boot' becomes 'kick' ('kick' can be a synonym of 'boot'**).
'back' put after 'kick' is 'KICKBACK'.
'for' is the link.
(Other definitions for kickback that I've seen before include "(Illicit) confidential payment to facilitator" , "Illegal payment" , "special gift" , "Bribe paid by seller to purchasing agent" , "Underhand payment" .)