The most common and most likely answer to this crossword clue is the 4 letter word BRAD
I've seen this crossword clue in The Daily Telegraph
B
R
A
D
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 BRAD mean?
BRAD noun- A thin, small nail, with a slight projection at the top on one side instead of a head, or occasionally with a small domed head, similar to that of an escutcheon pin.
- (elementary school usage) A paper fastener, a fastening device formed of thin, soft metal, such as shim brass, with a round head and a flat, split shank, which is spread after insertion in a hole in a stack of pages, in much the same way as a cotter pin or a split rivet.
- To attach using a brad.
- To upset the end of a rod inserted in a hole so as to prevent it from being pulled out, as when riveting.