The most common and most likely answer to this crossword clue is the 7 letter word WEAPONS
I've seen this crossword clue in The Daily Telegraph
W
E
A
P
O
N
S
More clues leading to the result WEAPONS
Buddy explains!
The straight part
We know that "could be used in self-defence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case could be used in self-defence = weapons.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 WEAPONS mean?
WEAPONS noun- An instrument of attack or defense in combat or hunting, e.g. most guns, missiles, or swords.
- An instrument or other means of harming or exerting control over another.
- A tool of any kind.
- An idiot, an oaf, a fool, a tool; a contemptible or incompetent person.