Bachelor with one mate's porcelain (4,5)
I believe the answer is:
bone china
'porcelain' is the definition.
(bone china is a kind of porcelain)
'bachelor with one mate's' is the wordplay.
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'with' says to put letters next to each other.
'mate' becomes 'china' (cockney rhyming slang, mate is china plate).
'b'+'one'+'china'='BONE CHINA'
(Other definitions for bone china that I've seen before include "Material from Potter" , "Delicate base for service" , "Form of white porcelain" , "Fine things perhaps thrown" , "eating off this?" .)