Opposed to foregone old appetizer (9)
I believe the answer is:
antipasto
'appetizer' is the definition.
(antipasto is a kind of appetizer)
'opposed to foregone old' is the wordplay.
'opposed to' becomes 'anti' (anti means opposing something).
'foregone' becomes 'past' (similar in meaning).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'anti'+'past'+'o'='ANTIPASTO'
(Other definitions for antipasto that I've seen before include "Appetiser, starter" , "first course" , "what to eat first" , "Appetizers in an Italian meal" , "Starter course in an Italian meal" .)