South Korean coins possibly obtained at great expense (4-3)
I believe the answer is:
hard-won
'south korean coins possibly obtained' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'at great expense' is the wordplay.
I cannot really see how this works, but
'at' could be 'on' (location) and 'on' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hard-won that I've seen before include "Gained with difficulty" , "Not easily achieved, took a lot of effort" , "Having been obtained with effort" , "Gained after much work and effort" .)