Concealed part of Poulenc overture (6)
I believe the answer is:
covert
'concealed' is the definition.
(similar in meaning)
'part of poulenc overture' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'COVERT' is hidden within 'poulenc overture'.
(Other definitions for covert that I've seen before include "Undercover, secret" , "Unacknowledged; thicket" , "Clandestine, furtive" , "Area of undergrowth in which animals hide" , "Concealed - flock of coots" .)