Melodies coming back from this Rialto sector (4)
I believe the answer is:
airs
'melodies' is the definition.
('air' can be a synonym of 'melody')
'coming back from this rialto sector' is the wordplay.
'coming back' says the letters should be written in reverse.
'from' says the answer is hidden in the clue.
'sria' can be found hidden inside 'this rialto sector'.
'sria' in reverse letter order is 'AIRS'.
(Other definitions for airs that I've seen before include "Voices" , "Strain's" , "Ventilates, say grievance" , "Pretentiousness" , "'Tunes, melodies (4)'" .)