wrestler waiting at ringside
In sumo, a wrestler who sits at the edge of the dohyō, ready to assist or to replace a competitor if needed.
控えの力士が土俵下で次の取組を待っている。
The wrestler waiting at ringside is waiting for the next bout below the dohyō.
Compound of 控え (ひかえ, 'waiting, reserve') + の (possessive particle) + 力士 (りきし, 'sumo wrestler').