The most common and most likely answer to this crossword clue is the 10 letter word LAUNDERING
I've seen this crossword clue in Financial Times
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More clues leading to the result LAUNDERING
Buddy explains!
The straight part
We know that "Where lucre’s filthy this cleans up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where lucre’s filthy this cleans up = laundering.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 LAUNDERING mean?
LAUNDERING verb- To wash; to wash, and to smooth with a flatiron or mangle; to wash and iron.
- To lave; to wet.
- (money) To disguise the source of (ill-gotten wealth) by various means.
- The act, or occupation, of one who launders; washing and ironing.