vendor at a sumo tournament
Refers to a vendor or shop selling food, drinks, and souvenirs within a sumo tournament venue. The reading すもうぢゃや uses the historical kana spelling ぢ for じ.
I bought yakitori and beer at a sumo tournament vendor.
A compound of 相撲 and 茶屋 “teahouse; refreshment vendor.” The reading ぢゃや reflects sequential voicing of the initial consonant of ちゃや.