The most common and most likely answer to this crossword clue is the 11 letter word IMMOBILISED
I've seen this crossword clue in Financial Times
I
M
M
O
B
I
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D
Buddy explains!
The straight part
We know that "incapable of shifting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case incapable of shifting = immobilised.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 IMMOBILISED mean?
IMMOBILISED verb- To render motionless; to stop moving or stop from moving.
- To modify a surface such that things will not stick to it