Officer allowed to entertain one associated with place of study (9)
I believe the answer is:
collegial
'associated with place of study' is the definition.
(associated with a college)
'officer allowed to entertain one' is the wordplay.
'officer' becomes 'col' (short for colonel).
'allowed' becomes 'legal' (I've seen this in another clue).
'to entertain' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'legal' enclosing 'i' is 'legial'.
'col'+'legial'='COLLEGIAL'
(Another definition for collegial that I've seen is " Pertaining to, say, Eton".)