Look unhappy, returning after a spray (7)
I believe the answer is:
aerosol
'spray' is the definition.
(thesaurus)
'look unhappy returning after a' is the wordplay.
'look' becomes 'lo'.
'unhappy' becomes 'sore' (**).
'returning' says the letters should be written backwards.
'after' is a charade indicator (letters next to each other).
'lo'+'sore'='losore'
'losore' reversed gives 'erosol'.
'erosol' after 'a' is 'AEROSOL'.
(Other definitions for aerosol that I've seen before include "fog?" , "Container with device for releasing contents as fine spray" , "O so real (anag.)" , "Air-spray" , "source of graffiti?" .)