The most common and most likely answer to this crossword clue is the 10 letter word INFLEXIBLE
I've seen this crossword clue in Financial Times
I
N
F
L
E
X
I
B
L
E
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 INFLEXIBLE mean?
INFLEXIBLE adjective- Not flexible; not capable of bending or being bent
- Not willing to change, e.g. one's opinion or habits