The most common and most likely answer to this crossword clue is the 7 letter word TEMPLAR
I've seen this crossword clue in Financial Times
T
E
M
P
L
A
R
More clues leading to the result TEMPLAR
Buddy explains!

The straight part
We know that "Crusading barrister" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case crusading barrister = templar.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 TEMPLAR mean?
TEMPLAR noun- A barrister having chambers in the Inner Temple or Middle Temple.
- Of or relating to a temple.