Asleep immediately, switched off? (3,4,1,5)
I believe the answer is:
out like a light
'asleep immediately' is the definition.
'switched off?' is the wordplay.
I cannot quite see how this works, but
'off?' could be 'out' and 'out' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for out like a light that I've seen before include "Quickly asleep" , "Having no problems sleeping" .)