The most common and most likely answer to this crossword clue is the 5 letter word NARKS
I've seen this crossword clue in The Guardian
N
A
R
K
S
More clues leading to the result NARKS
- Informers breaking ranks?
- Partially unmask rancidly repellent police spies
- Stephen King primarily published about troubles
- Bugs enter chest in opposing directions
- Grasses progressed up centre of workshop
- Winds up from opposite directions around ship
- Informers with partners impounding ship
- Annoying people breaking ranks?
- Bugs from opposing directions constricting chest
Buddy explains!

The straight part
We know that "police spies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case police spies = narks.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 NARKS mean?
NARKS noun- A narcotics squad police officer.
- A narcissist.
- A police spy or informer.
- An unpleasant person, especially one who makes things difficult for others.
- To watch; to observe.
- To serve or behave as a spy or informer.
- To annoy or irritate.
- To complain.
- (often imperative) To stop.