Ready for a good turn, foul defender (8)
I believe the answer is:
kickback
'ready for a good turn' is the definition.
(cash or 'ready' paid as a bribe)
'foul defender' is the wordplay.
'foul' becomes 'kick' (type of football foul).
'defender' becomes 'back' (I've seen this in other clues).
'kick'+'back'='KICKBACK'
(Other definitions for kickback that I've seen before include "strong reaction" , "Bribe - recoil" , "Recoil; illicit payment" , "Illegal payment" , "Forceful recoil" .)