The most common and most likely answer to this crossword clue is the 7 letter word BAILEYS
B
A
I
L
E
Y
S
More clues leading to the result BAILEYS
Buddy explains!

The straight part
We know that "Fortifications around, keep/liqueur" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fortifications around, keep/liqueur = baileys.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 BAILEYS mean?
BAILEYS noun- The outer wall of a feudal castle.
- The space immediately within the outer wall of a castle or fortress.
- (in certain proper names) A prison or court of justice.