Department advocating matricide? (6)
I believe the answer is:
domain
'department' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(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" .)