Food for growing insect (4)
I believe the answer is:
grub
This could be a double definition.
'food' is the first definition.
(I know that food can be written as grub)
'growing insect' is the second definition.
'grub' can be an answer for 'insect' (a grub is an insect larva). I'm unsure of the 'growing' bit.
'for' is the link.
Can you help me to learn more?
(Other definitions for grub that I've seen before include "Slangy food or kind of larva" , "Table needs" , "Dig (up); hack writers' Street" , "Eats - larva" , "Dig - maggot - food" .)