Weapons farmer is waving? (8)
I believe the answer is:
firearms
'weapons' is the definition.
(firearm is a kind of weapon)
'farmer is waving?' is the wordplay.
'waving?' indicates anagramming the letters (letters wave around).
'farmer'+'is'='farmeris'
'farmeris' anagrammed gives 'FIREARMS'.
(Other definitions for firearms that I've seen before include "Rifles, guns, pistols etc" , "Weaponry" , "they can kill people" , "Weapons" , "Portable guns" .)