The most common and most likely answer to this crossword clue is the 2 letter word PM
I've seen this crossword clue in Independent
P
M
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 PM mean?
PM adverb- After noon (used after a time to indicate it is between noon and midnight, i.e., in the afternoon, evening or night as opposed to the morning)
- After death