Jumbo Cryptic 898

[endanger33]

12d notable feature of Chicago, namely music in the strongest of hits 11 (first & last S)

23a A princess in opera? Either G&S or Verdi 4 ?i??

21a Second partner returned to BBC with a change of heart concerning pronunciation unit 8 s???????

40a makes a mistake, getting nought in exam 6 ?r?p??

9d Head of aristocratic line in Scilian city offers wife to Claudius 9 m?s??????

[sandyRoe]

23a Aida
40a Tripos

[Calibax]

23a Aida
40a Tripos
9d Messalina

[glasman]

23a Aida

[sandyRoe]

9d Messalina

[Lie-in King]

12d Skyscrapers - sc(ilicet) (namely) + 'rap' (in) 'skyers' (hits)
23a Aida - (Verdi) & (Princess) Ida
21a Syllabic - s(econd) + ally + BiC (change of heart)
40a Trip-0-s
9d Messalina - a(ristocratic) + l(ine) (in) Messina

[civdm]

12d skyscrapers
21a syllabic S(econd) ALLY (reversed) = partner BIC (BBC with heart changed)

[endanger33]

thank you all!