Provincial party set up — food provided (3)
I believe the answer is:
pud
'food provided' is the definition.
(pudding)
'provincial party set up' is the wordplay.
'provincial party' becomes 'DUP' (Democratic Unionist Party in Northern Ireland).
'set up' shows that the letters should be reversed in order (in a down clue, letters go up).
'dup' back-to-front is 'PUD'.
(Other definitions for pud that I've seen before include "hand" , "duff?" , "Cooked sweet dish" .)