Philosopher thus keeps almost closed (5)
I believe the answer is:
stoic
'philosopher' is the definition.
(Stoic is an example)
'thus keeps almost closed' is the wordplay.
'thus' becomes 'sic' ('sic' can be a synonym of 'thus').
'keeps' means one lot of letters goes inside another.
'almost closed' becomes 'to' (I am not sure about this - if you are sure you should believe this answer much more).
'sic' placed around 'to' is 'STOIC'.
Can you help me to learn more?
(Other definitions for stoic that I've seen before include "Philosopher like Marcus Aurelius" , "Resigned" , "Person indifferent to pleasure or pain" , "Seeming unaffected by pleasure or pain" , "One who endures pain with equanimity" .)