Half a dime (6)
I believe the answer is:
nickel
'half a dime' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nickel that I've seen before include "US five cent piece" , "Element; five cents in US" , "Metallic element, Ni" , "5c coin" , "Coin worth half a dime" .)