Opera house cuts Callas calamitously (7)
I believe the answer is:
lascala
'opera' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'house cuts callas calamitously' is the wordplay.
'house' becomes 'a' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cuts' is an insertion indicator (some letters cut their way into a word).
'calamitously' indicates anagramming the letters (I've seen this in other clues).
'callas' with letters rearranged gives 'lscala'.
'a' placed within 'lscala' is 'LASCALA'.
Can you help me to learn more?
(Other definitions for lascala that I've seen before include "theatre" , "music venue" .)