The most common and most likely answer to this crossword clue is the 9 letter word CARMELITE
I've seen this crossword clue in The Guardian
C
A
R
M
E
L
I
T
E
More clues leading to the result CARMELITE
- Vehicle chosen by male member of religious order
- Prayer wheels crack after Mass
- Nun, peaceful-sounding type
- Brother smothering body part in 8 28
- Member of order chosen after appeal, not hard
- Sister declared fate easy to bear
- This writer has inaccurate article about friar
- Order lime cocktail in French menu
- Member of order chosen after Church's first division
- Time Clare trained to be nun
Buddy explains!

The straight part
We know that "Brother" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case brother = carmelite.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.