Socialist keeps fighting for compensation (6)
I believe the answer is:
reward
'compensation' is the definition.
(thesaurus)
'socialist keeps fighting' is the wordplay.
'socialist' becomes 'red' (red is a kind of socialist).
'keeps' means one lot of letters goes inside another.
'fighting' becomes 'war'.
'red' enclosing 'war' is 'REWARD'.
'for' is the link.
(Other definitions for reward that I've seen before include "Present given to mark service or good deed" , "Drawer (anag.)" , "Money offered for info" , "payment that's merited" , "Payment for services rendered" .)