The most common and most likely answer to this crossword clue is the 7 letter word VIBRATO
V
I
B
R
A
T
O
Buddy explains!
The straight part
We know that "vocal quavering" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vocal quavering = vibrato.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.
What does VIBRATO mean?
VIBRATO noun- The musical effect or technique where the pitch or frequency of a note or sound is quickly and repeatedly raised and lowered over a small distance for the duration of that note or sound.