Conflict among communists concerning prizes (7)
I believe the answer is:
rewards
'prizes' is the definition.
(I've seen this before)
'conflict among communists' is the wordplay.
'conflict' becomes 'war' (war is a kind of conflict).
'among' indicates putting letters inside (inserted letters are placed among others).
'communists' becomes 'reds' (red is a kind of communist).
'war' inserted into 'reds' is 'REWARDS'.
'concerning' acts as a link.
(Other definitions for rewards that I've seen before include "Gifts given in acknowledgement of behaviour or merits" , "They're given in recognition of merit or service" , "Prizes or remunerations" , "Gifts of appreciation" , "Payments made as marks of appreciation" .)