A provisional favourite is generous at heart with an aperitif (9)
I believe the answer is:
appetiser
'an aperitif' is the definition.
(I've seen this before)
'a provisional favourite is generous at heart' is the wordplay.
'provisional' becomes 'p' (this could be a standard abbreviation I've not previously seen).
'favourite' becomes 'pet' (synonyms).
'at heart' indicates the central letters.
The central letters of 'generous' are 'er'.
'a'+'p'+'pet'+'is'+'er'='APPETISER'
'with' is the link.
Can you help me to learn more?
(Other definitions for appetiser that I've seen before include "It's served before a meal" , "first course maybe" , "Aperitif" , "bonne bouche?" , "Antipasto" .)