The most common and most likely answer to this crossword clue is the 7 letter word TOURERS
I've seen this crossword clue in The Guardian
T
O
U
R
E
R
S
Buddy explains!

The straight part
We know that "Cars" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cars = tourers.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 TOURERS mean?
TOURERS noun- An open-top or soft-top motor car suitable for touring.
- A touring bicycle.