Successful song delivers beat (3)
I believe the answer is:
hit
I believe this clue is a double definition.
'successful song' is the first definition.
(I've seen this in another clue)
'beat' is the second definition.
(I've seen this before)
'delivers' acts as a link.
(Other definitions for hit that I've seen before include "Strike - great success!" , "The shot < to > beat" , "Successful song" , "Successful record/film" , "Popular record" .)