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