One suffering endless torpor (8)
I believe the answer is:
idleness
'torpor' is the definition.
(thesaurus)
'one suffering endless' is the wordplay.
'one' becomes 'i' (Roman numeral).
'suffering' is an anagram indicator.
'endless' with letters rearranged gives 'dleness'.
'i'+'dleness'='IDLENESS'
(Other definitions for idleness that I've seen before include "not working" , "Reluctance to work" , "Having a loaf" , "Sloth - there may be love in it" , "Inertia" .)