The most common and most likely answer to this crossword clue is the 10 letter word PETROLHEAD
I've seen this crossword clue in Financial Times
P
E
T
R
O
L
H
E
A
D
Buddy explains!
The straight part
We know that "a car enthusiast" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a car enthusiast = petrolhead.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 PETROLHEAD mean?
PETROLHEAD noun- A person who is overly reliant on the use of their car, resisting any suggestion to use other means of transport.
- A bogan who is overly fond of their car or motorbike and enjoys showing it off and making noise with it.
- A person involved in motor racing as either participant or dedicated spectator.
- A car enthusiast.