Not alert (6)
I believe the answer is:
asleep
'not alert' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for asleep that I've seen before include "In the arms of Hypnos" , "Having nodded off" , "coiled up?" , "Knitting up the ravelled sleeve of care" , "Dozing" .)