Belted out ditty about drink (7)
I believe the answer is:
sangria
'drink' is the definition.
(type of alcoholic drink)
'belted out ditty about' is the wordplay.
'belted out' becomes 'sang' (I've seen this in another clue).
'ditty' becomes 'air' (I've seen this in another clue).
'about' shows that the letters should be reversed in order.
'air' in reverse letter order is 'ria'.
'sang'+'ria'='SANGRIA'
(Other definitions for sangria that I've seen before include "Spanish sweetened wine drink" , "Spanish drink of red wine with soda water or lemonade" , "Drink - Iran gas (anag)" , "Mixed drink" , "Spanish spiced wine" .)