Official European court located in flawless administrative region (10)
I believe the answer is:
prefecture
'administrative region' is the definition.
'prefecture' can be an answer for 'region' (prefecture is a kind of region). I'm not sure about the 'administrative' bit.
'official european court located in flawless' is the wordplay.
'official' becomes 'ref' (match official in football, say).
'european' becomes 'E' (abbreviation e.g. EU).
'court' becomes 'ct' (abbreviation used in road names).
'located in' means one lot of letters goes inside another.
'flawless' becomes 'pure' (I've seen this before).
'ref'+'e'+'ct'='refect'
'refect' put within 'pure' is 'PREFECTURE'.
Can you help me to learn more?
(Other definitions for prefecture that I've seen before include "Regional administrative office" , "District under a governor" .)