Grass on dude in China (6)
I believe the answer is:
cathay
'china' is the definition.
(historical name for China)
'grass on dude' is the wordplay.
'grass' becomes 'hay' (hay is dried grass).
'on' is a charade indicator (letters next to each other).
'dude' becomes 'cat' (American slang for man, esp in Jazz).
'hay' after 'cat' is 'CATHAY'.
'in' acts as a link.
(Other definitions for cathay that I've seen before include "Name for China in medieval times" , "poetic land" , "Name for China in medieval Europe" , "China long ago" , "Old word for China" .)