A lot of criticism about old philosopher (5)
I believe the answer is:
stoic
'philosopher' is the definition.
(Stoic is an example)
I can't explain the rest of the clue.
(Other definitions for stoic that I've seen before include "the original Zeno?" , "Long-suffering type; follower of Zeno" , "Uncomplaining person" , "Athenian philosopher" , "One indifferent to fortune, pleasure and pain" .)