The most common and most likely answer to this crossword clue is the 4 letter word JOIN
I've seen this crossword clue in The Times
J
O
I
N
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 JOIN mean?
JOIN noun- An intersection of piping or wiring; an interconnect.
- An intersection of data in two or more database tables.
- The act of joining something, such as a network.
- The lowest upper bound, an operation between pairs of elements in a lattice, denoted by the symbol ∨.
- To connect or combine into one; to put together.
- To come together; to meet.
- To come into the company of.
- To become a member of.
- To produce an intersection of data in two or more database tables.
- To unite in marriage.
- To enjoin upon; to command.
- To accept, or engage in, as a contest.