Insect in a cloud (4)
I believe the answer is:
gnat
'insect in a cloud' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gnat that I've seen before include "Small, swarming insect" , "Small biter" , "Small biting flying insect" , "Small biting fly" , "Insect like small mosquito" .)