Housefly larva (6)
I believe the answer is:
maggot
'housefly larva' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for maggot that I've seen before include "Legless larva" , "youngster to fly" , "Lava of a fly" , "immature flyer" , "Fly larva" .)