American tune recalled part of opera? (4)
I believe the answer is:
aria
'part of opera?' is the definition.
('aria' is part of 'opera')
'american tune recalled' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'tune' becomes 'air' (air can mean a piece of music).
'recalled' is a reversal indicator (to recall can mean to bring something back).
'air' reversed gives 'ria'.
'a'+'ria'='ARIA'
(Other definitions for aria that I've seen before include "part of opera, maybe" , "Operatic song" , "Piece of music" , "Operatic air" , "Operatic vocal" .)