The most common and most likely answer to this crossword clue is the 6 letter word SOOTHE
I've seen this crossword clue in The Guardian
S
O
O
T
H
E
More clues leading to the result SOOTHE
- Calm man's after some smut
- Ambassador, found with smut, is calm
- Quiet woman, at heart excessively contrary
- Very old article brings comfort
- Calm woman keeping glasses close to cabinet
- Provide calming influence so others are content
- He’s too stupid to appease
- He’s too excited to become calm
- Calm down male faced with something falling down chimney?
- Black stuff? What’s taken up for comfort
Buddy explains!

The straight part
We know that "calm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case calm = soothe.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 SOOTHE mean?
SOOTHE verb- To restore to ease, comfort, or tranquility; relieve; calm; quiet; refresh.
- To allay; assuage; mitigate; soften.
- To smooth over; render less obnoxious.
- To calm or placate someone or some situation.
- To ease or relieve pain or suffering.
- To temporise by assent, concession, flattery, or cajolery.
- To bring comfort or relief.
- To keep in good humour; wheedle; cajole; flatter.
- To prove true; verify; confirm as true.
- To confirm the statements of; maintain the truthfulness of (a person); bear out.
- To assent to; yield to; humour by agreement or concession.