Disadvantage to hear a song (5)
I believe the answer is:
catch
I believe this clue is a triple definition!
'disadvantage' is the first definition.
('what's the catch?')
'to hear' is the second definition.
(catching is a kind of hearing)
'a song' is the third definition.
(old-fashioned type of musical composition)
(Other definitions for catch that I've seen before include "Arrest" , "Dismiss (batsman); break (in voice)" , "Get a grip on" , "Snag; be in time for (train)" , "Trap (a batsman?)" .)