Assuming food and drink is outside (5-2)

I believe the answer is:
stuck-up
'outside' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'assuming food and drink' is the wordplay.
I cannot quite see how this works, but
'food' could be 'tuck' (tuck can mean food) and 'tuck' is found in the answer.
'drink' could be 'sup' (to sup is to drink) and 'sup' is located in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for stuck-up that I've seen before include "Overly conceited or arrogant" , "Snooty" , "Hoity-toity" , "Snobbish, proud" , "Toffee-nosed" .)
