Unflappable (13)
'unflappable' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stoic that I've seen before include "Resilient philosopher" , "Seeming unaffected by pleasure or pain" , "philosophical type" , "Greek in school" , "Person indifferent to pleasure or pain" .)
'unflappable' is the definition.
(I know that unflappable can be written as imperturbable)
This is the entire clue.
(Other definitions for imperturbable that I've seen before include "Equanimous" , "Unruffled" , "Cool" , "Unflappable" , "Stoical" .)