The most common and most likely answer to this crossword clue is the 1 plus 4 plus 3 plus 7 letter word I SHOT THE SHERIFF
I've seen this crossword clue in Independent
I
S
H
O
T
T
H
E
S
H
E
R
I
F
F
More clues leading to the result I SHOT THE SHERIFF
Buddy explains!

The straight part
We know that "Vocal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vocal = i shot the sheriff.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.