The most common and most likely answer to this crossword clue is the 11 letter word IMPLAUSIBLE
I've seen this crossword clue in Financial Times
I
M
P
L
A
U
S
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 IMPLAUSIBLE mean?
IMPLAUSIBLE adjective- Not plausible; unlikely; dubious.