The most common and most likely answer to this crossword clue is the 8 letter word COLLARED
I've seen this crossword clue in The Daily Telegraph
C
O
L
L
A
R
E
D
More clues leading to the result COLLARED
Buddy explains!

The straight part
We know that "A clergyman may be/arrested" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a clergyman may be/arrested = collared.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 COLLARED mean?
COLLARED verb- To grab or seize by the collar or neck.
- To place a collar on, to fit with one.
- To seize, capture or detain.
- To preempt, control stringently and exclusively.
- (law enforcement) To arrest.
- To bind in conversation.
- To roll up (beef or other meat) and bind it with string preparatory to cooking.
- (BDSM) To bind (a submissive) to a dominant under specific conditions or obligations.
- Having a collar (or other encircling demarcation).