In contract, organ player (5)
I believe the answer is:
actor
'player' is the definition.
(synonyms)
'in contract organ' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ACTOR' is hidden in the letters of 'contract organ'.
(Other definitions for actor that I've seen before include "One in a play" , "One taking part" , "One with role" , "Stage-player" , "Gielgud, say" .)