Trick is to wake up with nothing missing (4)
I believe the answer is:
ruse
'trick' is the definition.
(I've seen this in another clue)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ruse that I've seen before include "Ploy, artifice" , "Artful ploy" , "trick played" , "Sure its a strange deception" , "Sure to be a trick" .)