The most common and most likely answer to this crossword clue is the 9 letter word TRIATHLON
I've seen this crossword clue in The Daily Telegraph
T
R
I
A
T
H
L
O
N
More clues leading to the result TRIATHLON
- 9 attempt to be heard by Irish town briefly
- Test cricket side welcomes extremely tough competition
- Perhaps halt intro for an athletic event
- Test about half of them on sport
- Art Hilton devised sports event
- Left in hot train, suffering — one needs lots of exercise!
- Most of the parts to test available for three races
- What a court in session has restraining a couple of thieves
- Difficult time, working round most of the athletic event
- Event at which Irish town mostly follows attempt on the radio
Buddy explains!

The straight part
We know that "athletics event" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case athletics event = triathlon.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 TRIATHLON mean?
TRIATHLON noun- An athletics event in which contestants compete in swimming, cycling and running in turn.
- A former Olympic athletics event in which contestants compete in long jump, shot put, and 100-yard dash.
- Generally, a sports event in which contestant compete in a combination of three sports.