State of prolonged unconsciousness (4)
I believe the answer is:
coma
'state of prolonged unconsciousness' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for coma that I've seen before include "State of insensibility" , "State of unconsciousness caused by illness" , "Deep trance" , "Unconsciousness from which person cannot be aroused" , "long sleep" .)