Mate hurt in side (4)
I believe the answer is:
team
'side' is the definition.
(a side is a sporting team)
'mate hurt' is the wordplay.
'hurt' indicates an anagram.
'mate' with letters rearranged gives 'TEAM'.
'in' acts as a link.
(Other definitions for team that I've seen before include "(Football) side" , "Side in sporting event" , "One side in a game" , "Squad; side" , "Group working together" .)