Alarm not starting properly (5)
I believe the answer is:
right
'properly' is the definition.
(synonyms)
'alarm not starting' is the wordplay.
'alarm' becomes 'fright' (both can mean fear or worry).
'not starting' means to remove the first letter.
'fright' with its first letter removed is 'RIGHT'.
(Other definitions for right that I've seen before include "Morally good, justifiable or acceptable" , "Genuine" , "Privilege" , "A person is entitled to it" , "Punch" .)