Lethargy at home I rate badly (7)
I believe the answer is:
inertia
'lethargy' is the definition.
(thesaurus)
'home i rate badly' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'badly' indicates anagramming the letters.
'i'+'rate'='irate'
'irate' is an anagram of 'ertia'.
'in'+'ertia'='INERTIA'
'at' is the link.
(Other definitions for inertia that I've seen before include "inclination not to budge" , "Admonish" , "Passiveness" , "Tendency to remain at rest or in steady motion" , "I retain (anag) - the tendency to retain same speed and direction" .)