The most common and most likely answer to this crossword clue is the 9 letter word RACETRACK
I've seen this crossword clue in The Guardian
R
A
C
E
T
R
A
C
K
More clues leading to the result RACETRACK
- Frightful racket car produces here?
- Car racket broken up in Newmarket
- People on line for Belmont Park, perhaps
- People follow a course
- A course people follow
- Circuit people follow
- People mark course
- People change course involving traditional school subject in competitive setting
- Excellent time maintained by reversing vehicles on grand circuit
Buddy explains!

The straight part
We know that "A course" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a course = racetrack.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 RACETRACK mean?
RACETRACK noun- A course over which any type of races are run.
- A characteristic circular erosion pattern in deposition processes.