Caterpillar or grub (5)
I believe the answer is:
larva
I believe this is a double definition.
'caterpillar' is the first definition.
(I've seen this in another clue)
'grub' is the second definition.
(I know that grub can be written as larva)
(Other definitions for larva that I've seen before include "Manage" , "Maggots" , "Insect in the first post-egg stage of its life" , "Immature stage of an insect" , "Caterpillar perhaps" .)