Policeman arresting Henry on crack quickly (4-4)

I believe the answer is:

chop-chop

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'quickly' is the definition.
(I know that quickly can be written as chop-chop)

'policeman arresting henry on crack' is the wordplay.
'policeman' becomes 'cop' (slang term).
'arresting' is an insertion indicator.
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'on crack' becomes 'chop' (I can't explain this - if you can you should believe this answer much more).
'cop' enclosing 'h' is 'chop'.
'chop'+'chop'='CHOP-CHOP'

Can you help me to learn more?

(Other definitions for chop-chop that I've seen before include "Hurry up!" , "Quickly!" , "Get a move on!" .)

I've seen this clue in The Independent.

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