Area DI observing rules very closely (8)

I believe the answer is:

district

'area' is the definition.
(thesaurus)

'di observing rules very closely' is the wordplay.
'observing rules very closely' becomes 'strict' (I've seen this before).
'di'+'strict'='DISTRICT'

(Other definitions for district that I've seen before include "Zone, area" , "Precinct, section" , "A quarter" , "Territorial division" , "Area, region" .)

I've seen this clue in The Telegraph.

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