Song - it could be used to promote a dance? (6)
I believe the answer is:
ballad
'song' is the definition.
(ballad is a kind of song)
I don't understand how the remainder of the clue works.
(Other definitions for ballad that I've seen before include "Song that tells a story" , "Narrative song of popular origin" , "A simple or old song" , "Folk song" , "delivered by singer" .)