The most common and most likely answer to this crossword clue is the 3 letter word SIC
I've seen this crossword clue in Financial Times
S
I
C
More clues leading to the result SIC
- Urge to attack, so it appears
- Thus stitch regularly disappears
- Endless excuse for being off work, and no mistake!
- So unwell — finishing early
- Is round about? Yes, really
- So speaker’s indisposed
- So the listener’s disgusted
- So out of sorts, almost
- Endless suffering: that’s right, though appears wrong
- Ill, abbreviated thus in Latin
Buddy explains!

The straight part
We know that "So" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case so = sic.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 SIC mean?
SIC verb- To mark with a bracketed sic.
- Thus; thus written; used to indicate, for example, that text is being quoted as it is from the source.
- To incite an attack by, especially a dog or dogs.
- To set upon; to chase; to attack.