The most common and most likely answer to this crossword clue is the 4 plus 6 letter word THAI BOXING
I've seen this crossword clue in The Times
T
H
A
I
B
O
X
I
N
G
More clues leading to the result THAI BOXING
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 = thai boxing.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.