Ring sport (4)
I believe the answer is:
sumo
'ring sport' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sumo that I've seen before include "one of the martial arts" , "Style of traditional Japanese wrestling" , "Japanese form of wrestling" , "Japanese wrestling sport of over-weight men" , "Japanese wrestling for huge men" .)