The most common and most likely answer to this crossword clue is the 9 letter word PRECISIAN
I've seen this crossword clue in Financial Times
P
R
E
C
I
S
I
A
N
Buddy explains!
The straight part
We know that "pedant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pedant = precisian.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 PRECISIAN mean?
PRECISIAN noun- A religious purist; a Puritan.
- Someone who strictly observes the rules; a pedant or stickler.