Still shuts up an alarm (5)
I believe the answer is:
panic
'alarm' is the definition.
(alarm can mean panic or worry)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for panic that I've seen before include "Fearful confusion" , "Grass" , "Alarm - terror" , "Sudden overpowering fright" , "general alarm" .)