Gnats (6)
I believe the answer is:
midges
'gnats' is the definition.
(midge is a kind of gnat)
This is all the clue.
(Other definitions for midges that I've seen before include "Small gnatlike insects" , "Tiny insects" , "Small biting flies" , "Small flies that swarm near water" , "Mosquito-like flies, gnats" .)