Instigator of heavy metal in bell (10)
I believe the answer is:
ringleader
'instigator' is the definition.
(ringleader is a kind of instigator)
'heavy metal in bell' is the wordplay.
'heavy metal' becomes 'lead' (I've seen this before).
'in' is an insertion indicator.
'bell' becomes 'ringer' (I've seen this before).
'lead' put within 'ringer' is 'RINGLEADER'.
'of' is the link.
(Other definitions for ringleader that I've seen before include "brains" , "Chief mischief-maker" , "firebrand" , "Chief mischief maker" , "Main villain" .)