The most common and most likely answer to this crossword clue is the 8 plus 5 letter word NATIONAL GUARD
I've seen this crossword clue in The Daily Telegraph
N
A
T
I
O
N
A
L
G
U
A
R
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.