The most common and most likely answer to this crossword clue is the 2 plus 3 plus 5 letter word IN BAD TASTE
I've seen this crossword clue in The Guardian
I
N
B
A
D
T
A
S
T
E
More clues leading to the result IN BAD TASTE
Buddy explains!
The straight part
We know that "How vulgar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case how vulgar = in bad taste.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.