Metal charm found in Northern Ireland? I'm not sure (7)
I believe the answer is:
niobium
'metal' is the definition.
(metallic element)
'charm found in northern ireland? i'm not sure' is the wordplay.
'charm' becomes 'obi' (also obeah, type of sorcery).
'found in' is an insertion indicator.
'northern ireland?' becomes 'NI' (abbreviation).
'i'm not sure' becomes 'um' (expression of hesitation).
'ni'+'um'='nium'
'obi' inserted into 'nium' is 'NIOBIUM'.
(Other definitions for niobium that I've seen before include "Silver-grey metallic element" , "Silvery-grey metal, Nb" , "Superconductive element" , "Chemical element, Nb" , "Silver-grey metal, Nb" .)