The most common and most likely answer to this crossword clue is the 8 letter word BASTILLE
I've seen this crossword clue in The Sunday Telegraph
B
A
S
T
I
L
L
E
More clues leading to the result BASTILLE
- Graduate motionless beside European fortress
- Be touring a peaceful prison
- Be outside a quiet prison
- French can add butter to both sides of
- Foot of wall lit up in lower part of old Paris prison
- Work the land in infamous prison
- French fortress, HQ until captured
- Pour fat over wretched French jail
- Drawer of cash occupying vile prison
- Work in vile Parisian prison
Buddy explains!
The straight part
We know that "Old prison" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old prison = bastille.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.