Stern with more than 500 in this region (8)
I believe the answer is:
district
'500 in this region' is the definition.
'district' can be an answer for 'region' (district is a kind of region). I'm unsure of the '500 in this' bit.
'stern with more than' is the wordplay.
'stern' becomes 'strict' (synonyms).
'with' means one lot of letters go next to another.
'more than' becomes 'di' (I am not sure about this - if you are sure you should believe this answer much more).
'strict' put after 'di' is 'DISTRICT'.
Can you help me to learn more?
(Other definitions for district that I've seen before include "Locality" , "Region marked off for administrative or other purposes" , "Area of a town or city" , "Precinct, section" , "Area of town/country" .)