The most common and most likely answer to this crossword clue is the 9 letter word GUARDSMAN
I've seen this crossword clue in The Times
G
U
A
R
D
S
M
A
N
More clues leading to the result GUARDSMAN
Buddy explains!
The straight part
We know that "Soldier" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case soldier = guardsman.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.
What does GUARDSMAN mean?
GUARDSMAN noun- A person, especially a soldier, who is on guard.
- A member of the National Guard.
- A member of a Guards regiment.