A large weapon creates terror (5)
I believe the answer is:
alarm
'terror' is the definition.
(thesaurus)
'a large weapon' is the wordplay.
'large' becomes 'l'.
'weapon' becomes 'arm' (I've seen this before).
'a'+'l'+'arm'='ALARM'
'creates' acts as a link.
(Other definitions for alarm that I've seen before include "Frighten or startle" , "Noise giving warning" , "Shock; danger signal" , "Feeling of fear" , "Device sounding danger" .)