Some Korean mineral (3)
I believe the answer is:
ore
'mineral' is the definition.
(I know that ore is a type of mineral)
'some korean' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ORE' can be found hidden inside 'korean'.
(Other definitions for ore that I've seen before include "Mineral-bearing rock" , "Metal-bearing rock or mineral" , "Mineral or metal source" , "Naturally occurring mineral" , "Mineral - Scandinavian money" .)