Sort of plate, mate (5)
I believe the answer is:
china
'mate' is the definition.
(cockney rhyming slang, mate is china plate)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for china that I've seen before include "High quality porcelain" , "Delicate porcelain form Orient?" , "Household tableware" , "Ceramics; country" , "It's fragile, though its economy is not!" .)