The most common and most likely answer to this crossword clue is the 3 letter word NIX
I've seen this crossword clue in Independent
N
I
X
Buddy explains!
The straight part
We know that "0" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 0 = nix.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 NIX mean?
NIX noun- Nothing.
- To make something become nothing; to reject or cancel.
- To destroy or eradicate.
- A treacherous water-spirit; a nixie.