Revealed orchestra's first duet played ... (5)
I believe the answer is:
outed
'revealed' is the definition.
(outing is a kind of revealing)
'orchestra's first duet played' is the wordplay.
'orchestra's first' becomes 'o' (1st letter of 'orchestra').
'played' indicates an anagram.
'duet' with letters rearranged gives 'uted'.
'o'+'uted'='OUTED'
(Other definitions for outed that I've seen before include "Exposed in public" , "Exposed against one's will" , "Revealed (someone) as gay" , "Revealed the homosexuality of (someone)" .)