Zeno follower (5)
I believe the answer is:
'zeno follower' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stoic that I've seen before include "Unemotional" , "One patient under misfortune" , "Phlegmatic type" , "Greek in school" , "One showing endurance during adversity" .)