Caterpillar? (5)
I believe the answer is:
larva
'caterpillar?' is the definition.
(caterpillar is a kind of larva)
This is the entire clue.
(Other definitions for larva that I've seen before include "early form" , "Immature life form" , "Immature form of caterpillar" , "Maggot" , "Animal in immature state" .)