Comatose snake encircling shelter (6)
I believe the answer is:
asleep
'comatose' is the definition.
(thesaurus)
'snake encircling shelter' is the wordplay.
'snake' becomes 'asp' (asp is a kind of snake).
'encircling' indicates putting letters inside.
'shelter' becomes 'lee' (I've seen this before).
'asp' enclosing 'lee' is 'ASLEEP'.
(Other definitions for asleep that I've seen before include "See, pal strangely is not awake" , "Conked out" , "Dozing" , "Dead to the world" , "Napping" .)