Old court letter exposed Group of Eight (7)
I believe the answer is:
octette
'group of eight' is the definition.
(I've seen this before)
'old court letter exposed' is the wordplay.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'court' becomes 'ct' (abbreviation used in road names).
'exposed' means to look at the middle letters (outside letters removed).
The middle letters of 'letter' are 'ette'.
'o'+'ct'+'ette'='OCTETTE'
(Other definitions for octette that I've seen before include "Eight musicians" , "Noted work" , "Group of eight" .)