Christopher, acting as an historic official (5)

I believe the answer is:

reeve

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'official' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for reeve that I've seen before include "magistrate of long ago" , "Female ruff; also a bailiff" , "Old official in Bruree, venerated" , "mate of the ruff" , "Pass a rope through a block" .)

I've seen this clue in the Evening Standard.

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