The most common and most likely answer to this crossword clue is the 6 letter word LAWMAN
I've seen this crossword clue in The Times
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More clues leading to the result LAWMAN
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The straight part
We know that "Sheriff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sheriff = lawman.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 LAWMAN mean?
LAWMAN noun- A lawspeaker: a declarer of the law.
- One of 12 magistrates in certain Danish boroughs of England empowered with soc and sac over their own households.
- The presiding justice of the supreme court.
- A man of the law: a lawyer.
- An officer of the law: a law-enforcement officer.