The most common and most likely answer to this crossword clue is the 6 letter word SMIRCH
I've seen this crossword clue in The Daily Telegraph
S
M
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H
More clues leading to the result SMIRCH
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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 SMIRCH mean?
SMIRCH noun- Dirt, or a stain.
- A stain on somebody's reputation.
- To dirty; to make dirty.
- To harm the reputation of; to smear or slander.
- A chirp of radiation power from an astronomical body that has a smeared appearance on its plot in the time-frequency plane (usually associated with massive bodies orbiting supermassive black holes)