Song for a soprano (4)
I believe the answer is:
aria
'song for a soprano' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aria that I've seen before include "Musical performance" , "Song for solo voice from an oratorio, cantata etc" , "part of opera, maybe" , "Opera solo" , "Operatic vocal" .)