Panic US city raised over weapon (5)
I believe the answer is:
alarm
'panic' is the definition.
(thesaurus)
'us city raised over weapon' is the wordplay.
'us city' becomes 'la'.
'raised' shows that the letters should be reversed in order.
'over' means one lot of letters go next to another.
'weapon' becomes 'arm' (I've seen this before).
'la' back-to-front is 'al'.
'al'+'arm'='ALARM'
(Other definitions for alarm that I've seen before include "Noise giving warning" , "Warning sound/device" , "Fright" , "Frighten or startle" , "Noise that wakes" .)