Rikishi's sport (4)
I believe the answer is:
sumo
'rikishi's sport' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sumo that I've seen before include "slappers fighting?" , "Jap. wrestling" , "Japanese wrestling for huge men" , "Large Japanese wrestler" , "Japanese wrestling with big fat men" .)