Lover's song (8)
I believe the answer is:
serenade
'lover's song' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for serenade that I've seen before include "Lover's song" , "Song to a lover" , "Sing (for someone on a balcony?)" , "Song often sung under a window" , "It's played or sung at a lover's window" .)