Greek philosopher who taught Aristotle (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
plato
(Other definitions for plato that I've seen before include "A plot (anag) (known to Aristotle?)" , "To pal up with Greek philosopher" , "Ancient Greek philosopher" , "Philosopher of ancient Greece" , "Moon crater named after Greek philosopher" .)