Pinch the Spanish metal (6)
I believe the answer is:
'metal' is the definition.
(nickel is a kind of metal)
'pinch the spanish' is the wordplay.
'pinch' becomes 'nick' (both can mean to steal).
'the spanish' becomes 'el' ('the' in Spanish).
(Other definitions for nickel that I've seen before include "Metallic element, Ni" , "Metallic element; US coin" , "Coin worth half a dime" , "very little money" , "Silvery white metal" .)