Scrap the hour for jazz! (7)
I believe the answer is:
ragtime
'jazz' is the definition.
(I've seen this before)
'scrap the hour' is the wordplay.
'scrap' becomes 'rag' (I've seen this in other clues).
'the hour' becomes 'time' (I've seen this in another clue).
'rag'+'time'='RAGTIME'
'for' is the link.
(Other definitions for ragtime that I've seen before include "Scott Joplin art form" , "Scott Joplin genre" , "Song and dance" , "Scott Joplin music style" , "musical style" .)