Note group having to adjust again (5)
I believe the answer is:
reset
'to adjust again' is the definition.
('set' can be a synonym for 'to adjust' so perhaps 'reset' is OK for 'to adjust again')
'note group' is the wordplay.
'note' becomes 're' (as in do-re-mi).
'group' becomes 'set' (both can mean a collection).
're'+'set'='RESET'
'having' is the link.
(Other definitions for reset that I've seen before include "Turn back to zero" , "do this to make adjustment" , "Put together again" , "Replace, resettle or put back again" , "question that's appeared in exam again" .)