Most prominent element metal bell contains? (10)
I believe the answer is:
ringleader
'most prominent element' is the definition.
'metal bell contains?' is the wordplay.
'metal' becomes 'lead' (lead is a kind of metal**).
'bell' becomes 'ringer' (I've seen this before).
'contains?' is an insertion indicator.
'lead' inserted within 'ringer' is 'RINGLEADER'.
(Other definitions for ringleader that I've seen before include "Chief mischief maker" , "Mastermind" , "brains" , "Chief mischief-maker" , "Chief troublemaker" .)