The most common and most likely answer to this crossword clue is the 5 letter word BASHO
I've seen this crossword clue in Financial Times
B
A
S
H
O
Buddy explains!

The straight part
We know that "wrestling tournament" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wrestling tournament = basho.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 BASHO mean?
BASHO noun- A sumo tournament of any kind