Greek attorney's originally in court (5)
I believe the answer is:
attic
'greek' is the definition.
(from ancient Athens or Attica)
'attorney's originally in court' is the wordplay.
'attorney' becomes 'att' (abbreviation for attorney).
'originally' says to take the initial letters.
The first letters of 'in court' is 'ic'.
'att'+'ic'='ATTIC'
(Other definitions for attic that I've seen before include "Small room at the top" , "Athenian - garret" , "Area at the top of the house" , "Greek - garret" , "Top chamber" .)