Giant of philosophy (5)
I believe the answer is:
plato
'giant of philosophy' 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 "Greek philosopher (The Republic)" , "A plot (anag) (known to Aristotle?)" , "Moon crater named after Greek philosopher" , "Ancient Greek philosopher" , "To pal up with Greek philosopher" .)