The most common and most likely answer to this crossword clue is the 8 letter word UNBUTTON
I've seen this crossword clue in Independent
U
N
B
U
T
T
O
N
More clues leading to the result UNBUTTON
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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 UNBUTTON mean?
UNBUTTON verb- To open (something) by undoing its buttons.
- To come open by having its buttons unfastened.