The most common and most likely answer to this crossword clue is the 1 letter word P
I've seen this crossword clue in The Guardian
P
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 P mean?
P noun- Abbreviation of penny; pence.
- Proton
- One of the many pieces of paper bound together within a book or similar document.
- One side of a paper leaf on which one has written or printed.
- Any record or writing; a collective memory.
- The type set up for printing a page.
- A screenful of text and possibly other content.
- A web page.
- A block of contiguous memory of a fixed length.
- A serving boy – a youth attending a person of high degree, especially at courts, as a position of honor and education.
- A youth employed for doing errands, waiting on the door, and similar service in households.
- A boy or girl employed to wait upon the members of a legislative body.
- (in libraries) The common name given to an employee whose main purpose is to replace materials that have either been checked out or otherwise moved, back to their shelves.
- A boy child.
- A contrivance, as a band, pin, snap, or the like, to hold the skirt of a woman’s dress from the ground.
- A track along which pallets carrying newly molded bricks are conveyed to the hack.
- A message sent to someone's pager.
- Any one of several species of colorful South American moths of the genus Urania.
- For each.
- To each, in each (used in expressing ratios of units).
- By the, by means of the, via the, through the.
- In accordance with.
- After; especially after a significant event that has long-term ramifications.
- Somewhat, fairly, quite; sometimes also (by meiosis) very.
- Prettily, in a pretty manner.
- To decorate with fringe or embroidered edge
- An inverted stitch producing ribbing etc
- To upset, to spin, capsize, fall heavily, fall headlong.
- To flow with a murmuring sound in swirls and eddies.
- To rise in circles, ripples, or undulations; to curl; to mantle.