The most common and most likely answer to this crossword clue is the 8 letter word UNFASTEN
I've seen this crossword clue in Independent
U
N
F
A
S
T
E
N
More clues leading to the result UNFASTEN
- Open quickly to be decanted into wonky funnel uncovered
- Loose bowels voided, Englishman likely to run ahead
- Open University flying course latterly in news
- French article covering couple of points about diet
- Open feast with nun dancing
- Release welcomed by nun; hast ended
- Open marriage? Promiscuous European has replaced Gussalufz, love!
- Open without cosier arrangement of surface tension
- Loose faun sent off
- Release aunt’s fine bust? Not I
Buddy explains!

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 UNFASTEN mean?
UNFASTEN verb- To detach from any connecting agency or link; to disconnect.
- To come unloosed or untied.