The most common and most likely answer to this crossword clue is the 3 letter word NIL
I've seen this crossword clue in The Times
N
I
L
More clues leading to the result NIL
- Nothing left at home? Quite the reverse
- Collar hasn't a zip
- Love Northern Ireland lake
- Zero in, turning attention away from earl
- Row endlessly about nothing
- Duck in long river, dropping tail
- Zero energy extracted from river
- In ruin I leave nothing
- Disappointing score on field, regularly!
- Line up briefly for nothing
Buddy explains!

The straight part
We know that "Zero" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case zero = nil.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 NIL mean?
NIL noun- Nothing; zero.