The most common and most likely answer to this crossword clue is the 8 plus 3 plus 6 letter word TROOPING THE COLOUR
T
R
O
O
P
I
N
G
T
H
E
C
O
L
O
U
R
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.