Tune from musical husband's forgotten (3)
I believe the answer is:
air
'tune' is the definition.
('air' can be a synonym of 'tune')
'musical husband's forgotten' is the wordplay.
'musical' becomes 'hair' (I've seen this before).
'husband' becomes 'h'.
'forgotten' suggests deleting specific letters.
'hair' with 'h' taken out is 'AIR'.
'from' acts as a link.
(Other definitions for air that I've seen before include "Vital thing" , "Gas mixture required for breathing" , "what emerges from singer's lungs?" , "It's a mixture mainly of oxygen and nitrogen" , "Ambience" .)