Rest of the song! (3)
I believe the answer is:
lay
I believe this is a double definition.
'rest' is the first definition.
(thesaurus)
'the song' is the second definition.
(lay is a kind of song)
'of' is the link.
(Other definitions for lay that I've seen before include "Of bird, produce egg" , "bed" , "Non-clerical, amateur" , "Arrange" , "gamble" .)