Met solo (4)
I believe the answer is:
aria
'met solo' 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 "Operatic song" , "Song, one from 'West Side Story' needing no introduction" , "Piece of music" , "selection of opera" , "Operatic air" .)