The most common and most likely answer to this crossword clue is the 5 letter word NAAFI
I've seen this crossword clue in The Daily Telegraph
N
A
A
F
I
More clues leading to the result NAAFI
- One — a halfwit — regularly seen in services canteen
- Part of Bologna a filthy mess, perhaps
- Inside taverna, a fine place to eat
- Banana a fiver? That has saved canteen!
- One admirer returns carrying a canteen
- Eatery’s providing motorists with nosh initially westbound
- Canteen – one up on Mayfair regularly
- Where those who serve may be served
- North American fellow gets into first-rate mess
- Sneak affair after regular visits in canteen
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 = naafi.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.