The most common and most likely answer to this crossword clue is the 4 letter word MUCK
I've seen this crossword clue in Independent
M
U
C
K
More clues leading to the result MUCK
Buddy explains!

The straight part
We know that "mess" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mess = muck.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 MUCK mean?
MUCK noun- (slimy) mud, sludge.
- Soft (or slimy) manure.
- Anything filthy or vile. Dirt; something that makes another thing dirty.
- Grub, slop, swill
- Money
- The pile of discarded cards.
- To shovel muck.
- To manure with muck.
- To do a dirty job.
- To pass, to fold without showing one's cards, often done when a better hand has already been revealed.