A new piece of advice regarding hors d’oeuvre (9)
I believe the answer is:
antipasto
'hors d'oeuvre' is the definition.
(both can mean a small meal)
'a new piece of advice regarding' is the wordplay.
'new' becomes 'n' (abbreviation as in New Testament NT).
'piece of advice' becomes 'tip' (a tip is a piece of advice).
'regarding' becomes 'as to' (as to that topic...).
'a'+'n'+'tip'+'asto'='ANTIPASTO'
(Other definitions for antipasto that I've seen before include "Italian appetiser" , "Starter course in an Italian meal" , "hors-d'oeuvre" , "Italian appetisers" , "Italian hors d'oeuvre" .)