The most common and most likely answer to this crossword clue is the 9 letter word ENTRAPPED
I've seen this crossword clue in The Guardian
E
N
T
R
A
P
P
E
D
Buddy explains!

The straight part
We know that "Unable to escape" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unable to escape = entrapped.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 ENTRAPPED mean?
ENTRAPPED verb- To catch in a trap or snare.
- To lure (someone), either into a dangerous situation, or into performing an illegal act.