The most common and most likely answer to this crossword clue is the 4 letter word JUDO
J
U
D
O
More clues leading to the result JUDO
- Only 50% fair — cheat in sport
- Judge at posh party for sport
- Sport which is played on board, jack replacing learner
- Judge duo performing martial art
- Half of arbiters initially opposed means of defence
- Sport‘s just done making first-half appearances
- After first half of month perform in sport
- Sport judge fired duo
- Martial art from Japan, for all to see and execute
- Heads of Japanese university departments overrate martial art
Buddy explains!

The straight part
We know that "sport" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sport = judo.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 JUDO mean?
JUDO noun- A Japanese martial art and sport adapted from jujutsu.