Not original policeman — last of constabulary (4)

I believe the answer is:

copy

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'not original' is the definition.
'copy' can be an answer for 'original' (thesaurus). I'm unsure of the 'not' bit.

'policeman last of constabulary' is the wordplay.
'policeman' becomes 'cop' (slang term).
'last of' suggests the final letters.
The last letter of 'constabulary' is 'y'.
'cop'+'y'='COPY'

Can you help me to learn more?

(Other definitions for copy that I've seen before include "Transcript" , "written for paper" , "Closely imitate" , "Facsimile" , "Replica; text for printing" .)

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