The most common and most likely answer to this crossword clue is the 9 letter word MODERATOR
I've seen this crossword clue in The Guardian
M
O
D
E
R
A
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R
More clues leading to the result MODERATOR
- Way artist turned bunk and chair
- Teenager once right about muse and minister
- Presiding officer, a Marxist, driven round in car
- Judge new motor dear
- Out of ministry, one inspiring run for presiding officer
- One examines failing trade in area in recession
- Church official departs on time in car
- Style associated with kind of bag or chair
- Style of an informant or a go-between
- One restoring order to a meeting primarily
Buddy explains!

The straight part
We know that "presiding officer/presiding officer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case presiding officer/presiding officer = moderator.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 MODERATOR mean?
MODERATOR noun- Someone who moderates
- The person who presides over a synod of a Presbyterian Church
- A substance (often water or graphite) used to decrease the speed of fast neutrons in a nuclear reactor and hence increase likelihood of fission
- A device used to deaden some of the noise from a firearm, although not to the same extent as a suppressor or silencer.
- An examiner at Oxford and Cambridge universities.
- At the University of Dublin, either the first (senior) or second (junior) in rank in an examination for the degree of Bachelor of Arts.
- Someone who supervises and monitors the setting and marking of examinations by different people to ensure consistency of standards.
- A mechanical arrangement for regulating motion in a machine, or producing equality of effect.
- A kind of lamp in which the flow of the oil to the wick is regulated.