Slow sentimental song (6)
I believe the answer is:
ballad
'slow sentimental song' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ballad that I've seen before include "Form of verse" , "Lay, narrative song" , "Simple song or poem" , "Narrative song with a recurrent refrain" , "delivered by singer" .)