Cups boy gold plates somewhere in Canada (8)
I believe the answer is:
labrador
'somewhere in canada' is the definition.
(I know this)
'cups boy gold plates' is the wordplay.
'cups' becomes 'bra' (as in the two cups of a bra).
'boy' becomes 'lad' (informal term for boy).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'plates' means one lot of letters goes inside another (to be plated in something is to be covered in it).
'lad'+'or'='lador'
'bra' placed inside 'lador' is 'LABRADOR'.
(Other definitions for labrador that I've seen before include "Breed of 1 across" , "Newfoundland area; dog" , "One that may have gone out with the guns" , "Canadian region and breed of dog" , "Part of Newfoundland" .)