Melody from American lifted atmosphere (4)
I believe the answer is:
aria
'melody' is the definition.
(thesaurus)
'american lifted atmosphere' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'lifted' is a reversal indicator (going up in down clue).
'atmosphere' becomes 'air' ('air' can be a synonym of 'atmosphere'**).
'air' written backwards gives 'ria'.
'a'+'ria'='ARIA'
'from' is the link.
(Other definitions for aria that I've seen before include "Musical performance" , "Song for solo voice from an oratorio, cantata etc" , "complex song" , "Type of song" , "Opera solo" .)