Unarmed, patrol population centres for serious crimes (10)

I believe the answer is:

atrocities

I'm a little stuck... Click here to teach me more about this clue!

'serious crimes' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Maybe there's a link between them I don't understand?

'unarmed patrol population centres' is the wordplay.
'unarmed patrol population' becomes 'atro' (I can't justify this - if you can you should give a lot more credence to this answer).
'centres' becomes 'cities' (I have seen 'urban centres' mean 'cities' so perhaps 'centres' could also mean 'cities').
'atro'+'cities'='ATROCITIES'

'for' is the link.

Can you help me to learn more?

(Other definitions for atrocities that I've seen before include "barbarous acts" , "Awful acts" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.