Formality of well-known Greek character with cape (11)

'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 located in the answer.
'cape' could be 'ness' (synonyms) and 'ness' is present in the answer.
The remaining letters 'chi' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'of' is the link.

Can you help me to learn more?