The most common and most likely answer to this crossword clue is the 5 letter word VROOM
V
R
O
O
M
More clues leading to the result VROOM
- Rev Vicar’s first study, say
- Big sound in very small space
- Rev’s sound study, maybe, in support of vicar at first
- Rev needs volume and space
- Computer simulation of old motor starting to rev
- Engine noise heard in space after victory
- Drive and energy — oddly very low in reverse
- Sound of Queen once with low backing?
- Noise of engine in very restricted space
- 23 Velocity and space contribute to high pitched noise
Buddy explains!

The straight part
We know that "to rev" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to rev = vroom.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 VROOM mean?
VROOM noun- The sound of an engine revving up.
- To move with great speed; to zoom.
- The sound of an engine revving up.