Cut use of heroin, finally going for Hitsville's No 1 (6)
I believe the answer is:
ignore
'cut' is the definition.
('ignore' can be a synonym of 'cut')
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ignore that I've seen before include "set aside" , "Deliberately take no notice" , "Cut head off" , "Dismiss" , "Fail to consider" .)