Other half once turning up with a weapon (3)
I believe the answer is:
axe
'weapon' is the definition.
(axe is a type of weapon)
'other half once turning up with a' is the wordplay.
'other half once' becomes 'ex' (ex-partner).
'turning up' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'ex' backwards is 'xe'.
'xe' put after 'a' is 'AXE'.
(Other definitions for axe that I've seen before include "Do away with" , "Dispense with" , "Tool for cutting, chopping" , "Cut (jobs)" , "Get rid of" .)