Nullify weapon, once called outside? (6)
I believe the answer is:
negate
'nullify' is the definition.
(I know that nullify is a kind of negate)
'weapon once called outside?' is the wordplay.
'weapon' becomes 'gat' (gat is a kind of weapon).
'once called' becomes 'nee' (I've seen this in another clue).
'outside?' is an insertion indicator (some letters go outside others).
'gat' put within 'nee' is 'NEGATE'.
(Other definitions for negate that I've seen before include "Show to be false" , "Render null or disprove" , "Disprove or nullify" , "Contradict" , "Countermand" .)