Device used in ensemble music (6)
I believe the answer is:
emblem
'device' is the definition.
(thesaurus)
'in ensemble music' is the wordplay.
'in' indicates the answer is hidden within the clue.
'EMBLEM' is hidden within 'ensemble music'.
'used' acts as a link.
(Other definitions for emblem that I've seen before include "Visible symbol of an abstract idea" , "Symbol, device that represents something" , "Symbolic representation on badge etc" , "Symbol, representative device" , "Symbolic object" .)