One filling roll for party (7)
I believe the answer is:
roister
'for party' is the definition.
(I've seen this before)
'one filling roll' is the wordplay.
'one' becomes 'i' (Roman numeral).
'filling' indicates putting letters inside.
'roll' becomes 'roster' (roll can mean a list or roster).
'i' placed into 'roster' is 'ROISTER'.
(Other definitions for roister that I've seen before include "riot" , "Be boisterous" , "Celebrate noisily" , "I rest or (anag) - engage in noisy merrymaking" , "Enfold" .)