It's mined in Korea (3)
I believe the answer is:
ore
'it's mined' is the definition.
I can't tell whether this defines the answer.
'in korea' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ORE' is hidden in the letters of 'korea'.
Can you help me to learn more?
(Other definitions for ore that I've seen before include "Mineral - Scandinavian money" , "it could be gold" , "Deposit of mine" , "15 down earth" , "Solid rock containing metal" .)