Dead to the world that comes to a boil (8)
I believe the answer is:
comatose
'dead to the world' is the definition.
(thesaurus)
'comes to a boil' is the wordplay.
'boil' indicates an anagram (I've seen 'boiling' mean this).
'comes'+'to'+'a'='comestoa'
'comestoa' anagrammed gives 'COMATOSE'.
'that' is the link.
(Other definitions for comatose that I've seen before include "Sandman called" , "Come to as in drowsy condition" , "Insensible or unconscious" , "Very drowsy, perhaps unconscious" , "In a drowsy or semi-conscious state" .)