The most common and most likely answer to this crossword clue is the 10 plus 7 letter word AÂ FAREWELL TOÂ ARMS
I've seen this crossword clue in The Guardian
A
Â
F
A
R
E
W
E
L
L
T
O
Â
A
R
M
S
Buddy explains!
The straight part
We know that "Its subject: in messy warfare, male lost" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case its subject: in messy warfare, male lost = a farewell to arms.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.