Lassitude, tiredness (8)
I believe the answer is:
lethargy
I believe this clue is a double definition.
'lassitude' is the first definition.
(I know that lassitude can be written as lethargy)
'tiredness' is the second definition.
(thesaurus)
(Other definitions for lethargy that I've seen before include "Inertia" , "Lack of energy and enthusiasm" , "state of apathy" , "Drowsy" , "Extreme lack of energy, listlessness" .)