Insect smell returned (4)
I believe the answer is:
gnat
'insect' is the definition.
(gnat is a kind of insect)
'smell returned' is the wordplay.
'smell' becomes 'tang' (I have seen 'Strong smell' mean 'tang' so perhaps 'smell' could also mean 'tang').
'returned' shows that the letters should be reversed in order.
'tang' reversed gives 'GNAT'.
(Other definitions for gnat that I've seen before include "Stinging insect" , "little irritation" , "Biting pest" , "Insect often hovering over stagnant water" , "Woodland area" .)