The most common and most likely answer to this crossword clue is the 8 plus 4 letter word ADHESIVE TAPE
I've seen this crossword clue in The Guardian
A
D
H
E
S
I
V
E
T
A
P
E
More clues leading to the result ADHESIVE TAPE
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.