The most common and most likely answer to this crossword clue is the 4 letter word MIMI
M
I
M
I
More clues leading to the result MIMI
- Note repeated in soprano's part
- In Herculaneum I'm inside sewer, doomed
- In opera she sings only one note or two
- Doomed sewer in Herculaneum I’m inside
- Puccini’s seamstress repeated note
- Curtailed ape’s role in Italian opera
- Article removed from Floridian city’s unfortunate sewer
- Girl sounding like a needy child
- Twice she tells us she’s coming back
- Two identical notes she sings in opera
Buddy explains!

The straight part
We know that "unfortunate sewer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unfortunate sewer = mimi.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.