The most common and most likely answer to this crossword clue is the 1 letter word X
I've seen this crossword clue in The Guardian
X
More clues leading to the result X
- Scan dead fish, say?
- Times certainly is after right photograph
- Gunmen stop axes penetrating beam
- X
- Draws symbol involving face of Malcolm X
- 1 OX LIVER/STEWART
- Special quality of vote for accepting parliamentary bill
- The Sun‘s probing axes Chief of Staff – pictures inside!
- Vote in favour of adopting decree produces that certain something
- They show you the bones of an unknown number of fish
Buddy explains!

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 X mean?
X adjective- Intersex or non-binary (in passports and identification documents).
- Suitable only for those aged 16 or (later) 18 years and over.
- (movie rating) Obscene.
- Used between the names of two characters to denote a ship, particularly in anime, manga, and video games.
- Used in place of and in artist collaborations.