Steal the Spanish coin (6)
I believe the answer is:
nickel
'coin' is the definition.
(nickel is a kind of coin)
'steal the spanish' is the wordplay.
'steal' becomes 'nick' (nick can informally mean to steal).
'the spanish' becomes 'el' ('the' in Spanish).
'nick'+'el'='NICKEL'
(Other definitions for nickel that I've seen before include "Metallic element; US coin" , "American 5-cent piece" , "US five cent piece" , "not worth much in America" , "Coin worth half a dime" .)