Solo for a soprano (4)
I believe the answer is:
aria
'solo for a soprano' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aria that I've seen before include "Piece of music" , "Operatic vocal" , "Operatic solo performance" , "Imitative art work" , "Vocal solo in a cantata etc" .)