Set up (like a police force?) (7)
I believe the answer is:
mounted
'set up like a police force?' is the definition.
I can't judge whether this defines the answer.
'set up like a police' is the wordplay.
'set up' becomes 'mount' (mounting is a kind of setting up).
'like a police' becomes 'ed' (I can't justify this - if you can you should believe this answer much more).
'mount'+'ed'='MOUNTED'
Can you help me to learn more?
(Other definitions for mounted that I've seen before include "Scaled" , "Prepared for exhibition" , "riding horses" , "Riding a horse" , "Rose" .)