The most common and most likely answer to this crossword clue is the 6 plus 1 plus 9 letter word INVADE > INVEIGHED
I've seen this crossword clue in The Guardian
I
N
V
A
D
E
>
I
N
V
E
I
G
H
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.