The most common and most likely answer to this crossword clue is the 6 plus 2 plus 1 plus 5 letter word SHADOW OF A DOUBT
S
H
A
D
O
W
O
F
A
D
O
U
B
T
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.