The most common and most likely answer to this crossword clue is the 5 letter word DOHYO
I've seen this crossword clue in Independent
D
O
H
Y
O
Buddy explains!
The straight part
We know that "the Japanese can compete here" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the japanese can compete here = dohyo.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does DOHYO mean?
DOHYO noun- The ring, made of compacted clay, in which a sumo wrestling match is held.