Game in pool, possibly (4)
I believe the answer is:
polo
'game' is the definition.
(polo is a kind of game)
'pool possibly' is the wordplay.
'possibly' indicates an anagram.
'pool' is an anagram of 'POLO'.
'in' is the link.
(Other definitions for polo that I've seen before include "explorer of the thirteenth century" , "Sport - mint - explorer" , "Horsey ball game" , "Game played on horses or in water" , "Top" .)