Bribe to stop advocate (8)
I believe the answer is:
kickback
'bribe' is the definition.
(I know that kickback is a type of bribe)
'stop advocate' is the wordplay.
'stop' becomes 'kick' (I've seen this before).
'advocate' becomes 'back'.
'kick'+'back'='KICKBACK'
'to' is the link.
(Other definitions for kickback that I've seen before include "Bribe - recoil" , "Recoil -- bung" , "Recoil; illicit payment" , "strong reaction" , "Forceful recoil" .)