Provide food and support — grub (11)
I believe the answer is:
caterpillar
'grub' is the definition.
(I've seen this before)
'provide food and support' is the wordplay.
'provide food' becomes 'cater' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'support' becomes 'pillar' (pillar is a kind of support).
'cater'+'pillar'='CATERPILLAR'
(Other definitions for caterpillar that I've seen before include "Tiny creature" , "looper, perhaps" , "8 17" , "sort of grub" , "He made do with a mushroom" .)