Element primarily identified in outstanding parent (6)
I believe the answer is:
osmium
'element' is the definition.
(chemical element)
'primarily identified in outstanding parent' is the wordplay.
'primarily' says to take the initial letters.
'in' is an insertion indicator.
'outstanding' becomes 'os' (accounting abbreviation).
'parent' becomes 'mum' (mum is a kind of parent).
The first letter of 'identified' is 'i'.
'os'+'mum'='osmum'
'i' put within 'osmum' is 'OSMIUM'.
(Other definitions for osmium that I've seen before include "Metal, the densest natural element (symbol Os)" , "Silvery-white metal, Os" , "Metallic element" , "Heaviest substance known" , "Chemical element" .)