The most common and most likely answer to this crossword clue is the 9 letter word TERSENESS
I've seen this crossword clue in The Times
T
E
R
S
E
N
E
S
S
More clues leading to the result TERSENESS
- Setter chosen — assess regularly for brevity
- Sneers set somehow to lead to an abrupt manner
- Abrupt manner of head supporting introduction of this language
- Otherwise stern, sees what’s lacking in long sentences
- Nasty sneers set to show abrupt manner
- Steer off-course approaching head – then it’s to the point
Buddy explains!
The straight part
We know that "brevity" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case brevity = terseness.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.