The most common and most likely answer to this crossword clue is the 9 letter word BUTTERFLY
I've seen this crossword clue in The Guardian
B
U
T
T
E
R
F
L
Y
More clues leading to the result BUTTERFLY
- Female taking in by bishop completely – a pretty little creature?
- Stroke goat, say, and run away
- Stroke goat, then run!
- Stroke goat then run away
- Cut of meat?
- Flattery given to sly dilettante?
- Book entirely about loud insect
- It’s what it does to another Rev
- Batsman’s opening, wholly in control of fine stroke
- 12, 15’s royal stock led to career
Buddy explains!

The straight part
We know that "It’s what it does to another Rev" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s what it does to another rev = butterfly.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 BUTTERFLY mean?
BUTTERFLY noun- A flying insect of the order Lepidoptera, distinguished from moths by their diurnal activity and generally brighter colouring.
- A use of surgical tape, cut into thin strips and placed across an open wound to hold it closed.
- The butterfly stroke.
- (in plural) A sensation of excited anxiety felt in the stomach.
- Someone seen as being unserious and (originally) dressed gaudily; someone flighty and unreliable.
- To cut (food) almost entirely in half and spread the halves apart, in a shape suggesting the wings of a butterfly.
- To cut strips of surgical tape or plasters into thin strips, and place across (a gaping wound) to close it.