Provide party supplies, support and grub (11)
I believe the answer is:
caterpillar
'grub' is the definition.
(I've seen this before)
'provide party supplies support' is the wordplay.
'provide' becomes 'cater' (catering is a kind of providing).
'party supplies support' becomes 'pillar' (I can't explain this - if you can you should give a lot more credence to this answer).
'cater'+'pillar'='CATERPILLAR'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for caterpillar that I've seen before include "He made do with a mushroom" , "Heavy tracked earth-moving vehicle" , "Tiny creature" , "Lepidopteran larva" , "Butterfly grub" .)