The most common and most likely answer to this crossword clue is the 4 letter word DIRK
I've seen this crossword clue in Independent
D
I
R
K
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 DIRK mean?
DIRK noun- A long Scottish dagger with a straight blade.
- (Midwest US) A penis; dork.
- (Midwest US) A socially unacceptable person; an oddball.
- To stab with a dirk.
- To darken.