Gangster with weapon creates panic (5)
I believe the answer is:
alarm
'panic' is the definition.
(thesaurus)
'gangster with weapon' is the wordplay.
'gangster' becomes 'al' (Al Capone).
'with' says to put letters next to each other.
'weapon' becomes 'arm' (I've seen this before).
'al'+'arm'='ALARM'
'creates' acts as a link.
(Other definitions for alarm that I've seen before include "Announcement of danger" , "Shock; danger signal" , "Agitate" , "Worried perhaps if one rings" , "Panicky arousal" .)