British boy bearing weapon (5)
I believe the answer is:
blade
'weapon' is the definition.
(I know that blade is a type of weapon)
'british boy bearing' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'boy' becomes 'lad' (informal term for boy).
'bearing' becomes 'e' (East, a compass bearing or direction).
'b'+'lad'+'e'='BLADE'
(Other definitions for blade that I've seen before include "Runner on an ice-skate" , "Leaf, of grass, say" , "Cutting part of grass?" , "London rail terminus" , "Flat part of an oar" .)