Weapon fired up in dispute (8)
I believe the answer is:
stiletto
'weapon' is the definition.
(stiletto is a kind of weapon)
'fired up in dispute' is the wordplay.
'fired' becomes 'lit' (set on fire).
'up' is a reversal indicator (in down clue: letters go upwards).
'in' is an insertion indicator.
'dispute' becomes 'setto' (I can't justify this - if you can you should give a lot more credence to this answer).
'lit' backwards is 'til'.
'til' inserted into 'setto' is 'STILETTO'.
Can you help me to learn more?
(Other definitions for stiletto that I've seen before include "Dagger with narrow blade, or a high heel" , "Narrow-bladed dagger" , "Dagger; tapered heel" , "A short knife, dagger or heel" , "One may have a stab" .)