Spanish agreement to import party food (6)
I believe the answer is:
scampi
'food' is the definition.
(scampi is a kind of food)
'spanish agreement to import party' is the wordplay.
'spanish agreement' becomes 'si' (Spanish for yes).
'to import' means one lot of letters goes inside another.
'party' becomes 'camp' (both can mean a group of people).
'si' enclosing 'camp' is 'SCAMPI'.
(Other definitions for scampi that I've seen before include "Cooked Norway lobsters" , "Cooked Norway lobster" , "Tasty prawns in batter" , "Breaded prawns" , "Large prawns as food" .)