The most common and most likely answer to this crossword clue is the 5 letter word BYLAW
I've seen this crossword clue in Financial Times
B
Y
L
A
W
Buddy explains!

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 BYLAW mean?
BYLAW noun- A local custom or law of a settlement or district.
- A rule made by a local authority to regulate its own affairs.
- A law or rule governing the internal affairs of an organization (e.g., corporation or business).