Some of the unconventional armaments cause a scare (5)
I believe the answer is:
alarm
'a scare' is the definition.
(I've seen this before)
'some of the unconventional armaments cause' is the wordplay.
'some of' indicates the answer is hidden within the clue.
'ALARM' is hidden in the letters of 'unconventional armaments cause'.
(Other definitions for alarm that I've seen before include "uneasiness" , "Burglar deterrent" , "Anxious awareness of danger" , "Noise that wakes" , "Consternation: kind of clock" .)