Plato's pupil (9)
I believe the answer is:
aristotle
'plato's pupil' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aristotle that I've seen before include "Great Greek philosopher of 4th century B.C." , "Greek logician" , "Peripatetic teacher" , "Old Greek teacher" , "philosophy tutor" .)