Fear of wake-up call (5)
I believe the answer is:
alarm
This clue is a double definition.
'fear' is the first definition.
(alarm is a kind of fear)
'wake-up call' is the second definition.
(as in an alarm clock)
'of' acts as a link.
(Other definitions for alarm that I've seen before include "Flap" , "Unnerve" , "Scare or worry" , "Announcement of danger" , "Daunt" .)