Provide food and support for butterfly larva (11)
I believe the answer is:
caterpillar
'butterfly larva' is the definition.
(I've seen this before)
'provide food and support' is the wordplay.
'provide food' becomes 'cater' (I've seen this before).
'and' means one lot of letters go next to another.
'support' becomes 'pillar' (pillar is a kind of support**).
'cater'+'pillar'='CATERPILLAR'
'for' acts as a link.
(Other definitions for caterpillar that I've seen before include "future monarch, perhaps" , "sort of grub" , "Butterfly/moth larva" , "Tiny creature" , "8 17" .)