See you, more than once, during overture to Ernani (3-3)
I believe the answer is:
bye-bye
'see you' is the definition.
(I've seen this before)
'more than once during overture to ernani' is the wordplay.
'more than once' shows that letters should be duplicated.
'during' becomes 'by' (I can't justify this - if you can you should believe this answer much more).
'overture to' suggests taking the first letters (overture can mean the beginning of something).
The initial letter of 'ernani' is 'e'.
'by'+'e'='bye'
'bye' duplicated is 'BYE-BYE'.
Can you help me to learn more?
(Other definitions for bye-bye that I've seen before include "See you" , "Ciao!" , "Childish farewell" , "Au revoir for juniors?" , "Ta-ta" .)