Cloud of insects (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
swarm
'cloud of insects' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for swarm that I've seen before include "New colonists" , "many insects" , "Mob" , "Large group of flying insects" , "Body of bees" .)