a well-mannered fellow, extremely ideal, being nobility formerly (10)

'nobility formerly' is the definition.
I can't tell whether this definition defines the answer.

'a well-mannered fellow extremely ideal being' is the wordplay.
'a well-mannered fellow' becomes 'gent' (I've seen this in another clue).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'being' becomes 'esse' (philosophical term for being or existence).
'ideal' with its middle removed is 'il'.
'gent'+'il'+'esse'='GENTILESSE'

Can you help me to learn more?