Socrates' student (5)
I believe the answer is:
plato
'socrates' student' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for plato that I've seen before include "Moon crater named after Greek philosopher" , "Greek philosopher, disciple of Aristotle" , "Teacher of Aristotle, pupil of Socrates" , "Greek character" , "Greek philosopher (The Republic)" .)