Sauce of amorous advance at American (7)
I believe the answer is:
passata
'sauce' is the definition.
(I've seen this before)
'amorous advance at american' is the wordplay.
'amorous advance' becomes 'pass' (I've seen this before).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'pass'+'at'+'a'='PASSATA'
'of' is the link.
(Other definitions for passata that I've seen before include "Sieved tomato puree" , "Tomato sauce" .)