The most common and most likely answer to this crossword clue is the 6 letter word UNBOLT
I've seen this crossword clue in The Guardian
U
N
B
O
L
T
More clues leading to the result UNBOLT
- Open a French type of sandwich with nothing in it
- Open, concealing nothing, unusually blunt
- Open a foreign roll of cloth
- Open champion from Jamaica knocks out South Africa and Italy
- Make fast? On the contrary
- Lout made a mess of covering note to open gate?
- Make insecure peacekeepers run away
- In trouble, ire leaves and settles. That’s release
Buddy explains!

The straight part
We know that "Make fast? On the contrary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case make fast? on the contrary = unbolt.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 UNBOLT mean?
UNBOLT verb- To unlock by undoing the bolts of.