The most common and most likely answer to this crossword clue is the 5 letter word DIRTY
I've seen this crossword clue in Financial Times
D
I
R
T
Y
More clues leading to the result DIRTY
Buddy explains!
The straight part
We know that "Foul" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foul = dirty.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 DIRTY mean?
DIRTY verb- To make (something) dirty.
- To stain or tarnish (somebody) with dishonor.
- To debase by distorting the real nature of (something).
- To become soiled.
- Unclean; covered with or containing unpleasant substances such as dirt or grime.
- That makes one unclean; corrupting, infecting.
- Morally unclean; obscene or indecent, especially sexually.
- Dishonourable; violating accepted standards or rules.
- Corrupt, illegal, or improper.
- Out of tune.
- Of color, discolored by impurities.
- Containing data needing to be written back to memory or disk.
- Carrying illegal drugs among one's possessions or inside of one's bloodstream.
- Used as an intensifier, especially in conjunction with "great".
- Sleety; gusty; stormy.
- Of an alcoholic beverage, especially a cocktail or mixed drink: served with the juice of olives.
- Of food, indulgent in an unhealthy way.
- In a dirty manner.