Bug brings back tang (4)
I believe the answer is:
gnat
'bug' is the definition.
(I know that gnat is a type of dipteran)
'back tang' is the wordplay.
'back' says the letters should be written in reverse.
'tang' written backwards gives 'GNAT'.
'brings' is the link.
(Other definitions for gnat that I've seen before include "Insect often hovering over stagnant water" , "mozzie" , "Stinging insect" , "Tang (anag.)" , "Small biter" .)