Fly alone (4)
I believe the answer is:
solo
'fly alone' is the definition.
(synonyms)
This is all the clue.
(Other definitions for solo that I've seen before include "Piece of music for one" , "Han - (Star Wars); fly unaccompanied" , "Fly aircraft" , "Performed by a single voice or instrument" , "(Piece performed) on one's own" .)