Sine qua non of Stoicism? Being strong on superior insolence (5,5,3)
I believe the answer is:
stiff upper lip
'sine qua non of stoicism?' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'strong on superior insolence' is the wordplay.
'strong' becomes 'stiff' (similar in meaning).
'on superior' becomes 'upper' (eg an upper house in a parliament. I am not sure about the 'on' bit.).
'insolence' becomes 'lip' (I've seen this in another clue).
'stiff'+'upper'+'lip'='STIFF UPPER LIP'
'being' acts as a link.
Can you help me to learn more?
(Other definitions for stiff upper lip that I've seen before include "Calm courage" , "Symbol of resolution in bad times" , "Uncomplaining stoicism needed" , "Evidence of stoicism" , "that may be under one's nose" .)