Song, melody (3)
I believe the answer is:
air
This clue is a double definition.
'song' is the first definition.
(I've seen this in another clue)
'melody' is the second definition.
(I know that melody can be written as air)
(Other definitions for air that I've seen before include "Divulge" , "Expose" , "a life support" , "Broadcast; gas" , "Ventilate with breathing gas" .)