Top horse race in China (5,5)
I believe the answer is:
crown derby
'china' is the definition.
(I've seen this before)
'top horse race' is the wordplay.
'top' becomes 'crown' (crown is a kind of top).
'horse race' becomes 'derby' (I've seen this in another clue).
'crown'+'derby'='CROWN DERBY'
'in' is the link.
(Other definitions for crown derby that I've seen before include "China? - with 22a" , "Service" , "Kind of porcelain" , "Brand of china" , "type of porcelain" .)