The most common and most likely answer to this crossword clue is the 6 letter word JUDGES
I've seen this crossword clue in Financial Times
J
U
D
G
E
S
More clues leading to the result JUDGES
- Critically appraises book
- Rules on book
- They try following Joshua
- Hardy character’s absorbing good Biblical text
- Book 16s gutted about Elbow missing lead
- Legal experts mostly fair about daughter, say, when had up
- First goal accepted by 2 special referees
- Forms an opinion on book
- Start to jab, poke after first and second tries
- Umpires cut short prank around dugout
Buddy explains!

The straight part
We know that "Rules on/book" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rules on/book = judges.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 JUDGES mean?
JUDGES noun- A public official whose duty it is to administer the law, especially by presiding over trials and rendering judgments; a justice.
- A person who decides the fate of someone or something that has been called into question.
- A person officiating at a sports event or similar.
- A person who evaluates something or forms an opinion.
- To sit in judgment on; to pass sentence on.
- To sit in judgment, to act as judge.
- To form an opinion on.
- To arbitrate; to pass opinion on something, especially to settle a dispute etc.
- To have as an opinion; to consider, suppose.
- To form an opinion; to infer.
- To criticize or label another person or thing.