Frighten, alarm (5)
I believe the answer is:
scare
This clue is a double definition.
'frighten' is the first definition.
(I know that frighten can be written as scare)
'alarm' is the second definition.
(I've seen this before)
(Other definitions for scare that I've seen before include "Health worry" , "Cause fright, alarm" , "Frighten, alarm" , "Panic" , "Greatly frighten" .)