Huge pile of cash, unused (4)
I believe the answer is:
mint
'unused' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for mint that I've seen before include "Excellent" , "Produce coins" , "Culinary herb" , "Herb to make money" , "Place where coin money is made" .)