Japan's national sport (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">japan's national sport</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sumo that I've seen before include "Kind of wrestling" , "foreign form of fighting" , "Style of traditional Japanese wrestling" , "Japanese wrestling with big fat men" , "Traditional Japanese wrestling by fat men" .)