The most common and most likely answer to this crossword clue is the 4 plus 2 plus 6 letter word KIRI TE KANAWA
K
I
R
I
T
E
K
A
N
A
W
A
Buddy explains!
The straight part
We know that "soprano" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case soprano = kiri te kanawa.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.