A caterpillar is something to eat (4)
I believe the answer is:
grub
I believe this is a double definition.
'a caterpillar' is the first definition.
(I've seen this before)
'is something to eat' is the second definition.
(grub can informally mean food)
(Other definitions for grub that I've seen before include "Common food" , "Nosh - larva" , "Beetle larva" , "Larva; food (sl.)" , "ferret > eats" .)