Department advocating matricide? (6)

I believe the answer is:

domain

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'department' is the definition.
(thesaurus)

I can't explain the remainder of the clue.

(Other definitions for domain that I've seen before include "District or area - or range of influence" , "Territory over which someone reigns" , "Special region, area of expertise" , "Field of thought or activity" , "Range of influence or field of activity" .)

I've seen this clue in The Sun and The Telegraph.

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