The most common and most likely answer to this crossword clue is the 9 letter word CONSTABLE
I've seen this crossword clue in The Times
C
O
N
S
T
A
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More clues leading to the result CONSTABLE
- Policeman’s list of wrong-doers
- Police officer in Cape, working with firm
- Force member to rip off firm
- Ancient study with group of horses he painted
- One who had a brush with the law?
- Officer studies information systematically displayed
- Copper, carbon and oxygen extremely unreactive
- Officer studies information, schematically presented
- Artist using copper
- Scan firm’s PC
Buddy explains!

The straight part
We know that "Officer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case officer = constable.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 CONSTABLE mean?
CONSTABLE noun- One holding the lowest rank in most Commonwealth police forces. (See also chief constable.)
- A police officer or an officer with equivalent powers.
- An officer of a noble court in the Middle Ages, usually a senior army commander. (See also marshal).
- The warden of a castle.
- A public officer, usually at municipal level, responsible for maintaining order or serving writs and court orders.
- (Channel Islands) An elected head of a parish (also known as a connétable)
- A large butterfly, Dichorragia nesimachus, family Nymphalidae, of Asia.
- To act as a constable or policeman.