The most common and most likely answer to this crossword clue is the 3 letter word YER
I've seen this crossword clue in The Guardian
Y
E
R
Buddy explains!
The straight part
We know that "solver’s somewhat vulgar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case solver’s somewhat vulgar = yer.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 YER mean?
YER adverb- Pronunciation spelling of yeah, yes.
- (object pronoun) The people spoken, or written to, as an object.
- (reflexive pronoun) (To) yourselves, (to) yourself.
- (object pronoun) The person spoken to or written to, as an object. (Replacing thee; originally as a mark of respect.)
- (subject pronoun) The people spoken to or written to, as a subject. (Replacing ye.)
- (subject pronoun) The person spoken to or written to, as a subject. (Originally as a mark of respect.)
- (indefinite personal pronoun) Anyone, one; an unspecified individual or group of individuals (as subject or object).
- Either of the letters ъ and ь in Cyrillic alphabets, which originally represented phonemically the ultra-short vowels in Slavic languages.