Dispute worker is a player (10)
I believe the answer is:
contestant
'player' is the definition.
(I've seen this before)
'dispute worker' is the wordplay.
'dispute' becomes 'contest' (I've seen this in another clue).
'worker' becomes 'ant' (worker is a type of ant).
'contest'+'ant'='CONTESTANT'
'is a' acts as a link.
(Other definitions for contestant that I've seen before include "Entrant" , "Competitor" , "One entering a competition" , "One in quiz" , "Player" .)