The most common and most likely answer to this crossword clue is the 9 letter word LANDMINES
I've seen this crossword clue in Financial Times
L
A
N
D
M
I
N
E
S
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The straight part
We know that "Weapons" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weapons = landmines.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 LANDMINES mean?
LANDMINES noun- A mine that is placed on land and designed to explode when stepped upon or touched.