The most common and most likely answer to this crossword clue is the 7 letter word SUNROOF
I've seen this crossword clue in The Daily Telegraph
S
U
N
R
O
O
F
Buddy explains!
The straight part
We know that "If it gets too hot, one may go back in the car" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case if it gets too hot, one may go back in the car = sunroof.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 SUNROOF mean?
SUNROOF noun- A fixed or operable opening in a vehicle roof (car or truck) which allows fresh air and/or light to enter the passenger compartment. A sunroof may include a transparent or opaque panel and may be manually operated or power driven.