The most common and most likely answer to this crossword clue is the 9 letter word OUBLIETTE
O
U
B
L
I
E
T
T
E
More clues leading to the result OUBLIETTE
- Dungeon built to keep unclothed criminal
- Be let out I fancy from dungeon
- Where French and British elite start to torture revolutionary cell
- Lout, I bet, upset close to austere place of incarceration
- Rest in uncertainty after heading off to the empty dark cell
- Dungeon? Yes in Paris, lawyer is trapped with setter essentially
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 OUBLIETTE mean?
OUBLIETTE noun- A dungeon only accessible by a trapdoor at the top.