Respond to the alarm clock (5)
I believe the answer is:
arise
'respond to the alarm clock' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arise that I've seen before include "Become apparent" , "Emerge" , "Happen" , "Get to one's feet" , "W B Yeats: 'I will . . . . . and go now'" .)