The most common and most likely answer to this crossword clue is the 5 letter word PLONK
I've seen this crossword clue in The Guardian
P
L
O
N
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 PLONK mean?
PLONK noun- The sound of something solid landing.
- To set or toss (something) down carelessly.
- To automatically ignore a particular poster.
- (followed by a location) Precisely and forcefully.
- The sound made by something solid landing.
- The supposed sound of adding a user to one's killfile.
- Cheap or inferior everyday wine.
- AC Plonk
- A female police constable.