Japanese form of wrestling (4)
I believe the answer is:
sumo
'japanese form of wrestling' 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 "Traditional Japanese wrestling by fat men" , "Style of traditional Japanese wrestling" , "Jap. wrestling" , "one of the martial arts" , "slappers fighting?" .)