The most common and most likely answer to this crossword clue is the 3 letter word POO
P
O
O
Buddy explains!

The straight part
We know that "Scoff at" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case scoff at = poo.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 POO mean?
POO noun- Feces.
- A piece of feces or an act of defecation.
- Cannabis resin.
- Champagne.
- To defecate.
- To dirty something with feces.
- Expressing annoyance, frustration, etc.: a minced oath for 'shit'.
- Short for shampoo.
- An instance of saying "pooh".
- To say "pooh".
- To say "pooh" to.
- Expressing dismissal, contempt, impatience, etc.
- Expressing disgust at an unpleasant smell.
- Short for shampoo.