The most common and most likely answer to this crossword clue is the 6 letter word WHITEN
I've seen this crossword clue in The Daily Telegraph
W
H
I
T
E
N
More clues leading to the result WHITEN
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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 WHITEN mean?
WHITEN verb- (To cause) to become white or whiter; to bleach or blanch.