Quick raid in which coppers take part (5)
I believe the answer is:
rapid
'quick' is the definition.
(synonyms)
'raid in which coppers take part' is the wordplay.
'in which' means one lot of letters goes inside another.
'coppers take part' becomes 'p' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'raid' placed around 'p' is 'RAPID'.
Can you help me to learn more?
(Other definitions for rapid that I've seen before include "Express" , "Fast, quick" , "Happening at great speed" , "Electrical connector" , "Prompt" .)