Formality of well-known Greek character with cape (11)
I believe the answer is:
starchiness
'formality' is the definition.
(I've seen this in another clue)
'well-known greek character with cape' is the wordplay.
I cannot really understand how this works, but
'character' could be 'star' (I have seen 'Leading character' mean 'star' so perhaps 'character' could also mean 'star') and 'star' is present in the answer.
'cape' could be 'ness' (synonyms) and 'ness' is found within the answer.
The remaining letters 'chi' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'of' acts as a link.
Can you help me to learn more?
(Another definition for starchiness that I've seen is " Stiffness of manner".)