The most common and most likely answer to this crossword clue is the 11 letter word UNEXPLAINED
I've seen this crossword clue in The Daily Telegraph
U
N
E
X
P
L
A
I
N
E
D
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 UNEXPLAINED mean?
UNEXPLAINED adjective- Not explained. Of unknown cause or origin.