Happened by chance to ring, interrupted by heavy metal (6)
I believe the answer is:
befell
'happened by chance' is the definition.
(befall can mean to happen by accident)
'ring interrupted by heavy metal' is the wordplay.
'ring' becomes 'bell' (both can mean to call on the phone).
'interrupted by' is an insertion indicator.
'heavy metal' becomes 'Fe' (chemical symbol for iron).
'bell' enclosing 'fe' is 'BEFELL'.
'to' is the link.
(Other definitions for befell that I've seen before include "Happened, came to pass" , "Happened to (someone)" .)