The most common and most likely answer to this crossword clue is the 7 letter word INKHORN
I've seen this crossword clue in Financial Times
I
N
K
H
O
R
N
More clues leading to the result INKHORN
Buddy explains!
The straight part
We know that "Pedantic/writer might use one" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pedantic/writer might use one = inkhorn.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 INKHORN mean?
INKHORN noun- A small portable container, often made of horn, used to carry ink.
- (used attributively, of vocabulary) Pedantic, obscurely scholarly.