Metal - US coin (6)
I believe the answer is:
nickel
This clue is a double definition.
'metal' is the first definition.
(nickel is a kind of metal)
'us coin' is the second definition.
(five cent coin in the US)
(Other definitions for nickel that I've seen before include "Coin worth half a dime" , "Silvery-white metal" , "An American 5-cent coin" , "Silvery white metal" , "5c coin" .)