The most common and most likely answer to this crossword clue is the 11 letter word SENTENTIOUS
I've seen this crossword clue in The Times
S
E
N
T
E
N
T
I
O
U
S
Buddy explains!
The straight part
We know that "in brief" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in brief = sententious.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 SENTENTIOUS mean?
SENTENTIOUS adjective- Full of meaning.
- Using as few words as possible; pithy and concise.
- Tending to use aphorisms or maxims, especially given to trite moralizing.