Counterpart in game (5)
I believe the answer is:
match
I believe this clue is a double definition.
'counterpart' is the first definition.
(I know that match is a type of counterpart)
'game' is the second definition.
(eg a football match)
'in' is the link.
(Other definitions for match that I've seen before include "Sporting event" , "Tally; game" , "Formal contest - game" , "Partnership" , "Game; lighter" .)