One whose duty is to be systematic? (7)

I believe the answer is:

orderly

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'systematic?' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for orderly that I've seen before include "Well-regulated" , "He should leave the ward neat" , "Systematically, not haphazard" , "Hospital or military attendant" , "An officer's servant, tidy chap" .)

I've seen this clue in the Evening Standard.

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