Playing in duet together (6)
I believe the answer is:
united
'together' is the definition.
(thesaurus)
'playing in duet' is the wordplay.
'playing' indicates an anagram.
'in'+'duet'='induet'
'induet' is an anagram of 'UNITED'.
(Other definitions for united that I've seen before include "Agreed" , "cooperative" , "See 9" , "Of like mind" , "Made one" .)