Collaborator with McCoist? (4)
I believe the answer is:
ally
'collaborator' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ally that I've seen before include "Co-operating person or nation" , "Friend and colleague" , "Band together" , "often helpful when cluing adverbs" , "Crony" .)