Scares almost everyone with weapons (6)
I believe the answer is:
alarms
'scares' is the definition.
(alarming is a kind of scaring)
'almost everyone with weapons' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'everyone' becomes 'all' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'weapons' becomes 'arms' ('arm' can be a synonym of 'weapon').
'all' with its last letter taken off is 'al'.
'al'+'arms'='ALARMS'
(Other definitions for alarms that I've seen before include "Danger signals" , "Warning sounds" , "Devices to signal danger" , "is scary" , "rattles" .)