Inactivity at home I rate terrible (7)
I believe the answer is:
inertia
'inactivity' is the definition.
(I know that inactivity can be written as inertia)
'home i rate terrible' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'terrible' is an anagram indicator.
'i'+'rate'='irate'
'irate' anagrammed gives 'ertia'.
'in'+'ertia'='INERTIA'
'at' acts as a link.
(Other definitions for inertia that I've seen before include "Lethargy" , "Resistance to change" , "Resistance to movement" , "Disinclination to move" , "Apathetic state" .)