Old man left China (3)
I believe the answer is:
pal
'china' is the definition.
(china plate is Cockney rhyming slang for mate)
'old man left' is the wordplay.
'old man' becomes 'pa' (both can mean someone's father).
'left' becomes 'l' (common abbreviation).
'pa'+'l'='PAL'
(Other definitions for pal that I've seen before include "Mate, informal friend" , "Mate, buddy" , "Bud" , "Brother" , "China" .)