Guide to fingering a brutal criminal in note (9)
I believe the answer is:
tablature
'guide to fingering' is the definition.
(I've seen this before)
'a brutal criminal in note' is the wordplay.
'criminal' indicates anagramming the letters.
'in' indicates putting letters inside.
'note' becomes 'te' (**).
'a'+'brutal'='abrutal'
'abrutal' with letters rearranged gives 'ablatur'.
'ablatur' put inside 'te' is 'TABLATURE'.
(Other definitions for tablature that I've seen before include "Guide to fingering" , "musical notation" , "Form of music notation" .)