Changes in it are due to inactivity (7)
I believe the answer is:
inertia
'inactivity' is the definition.
(thesaurus)
'changes in it are' is the wordplay.
'changes' is an anagram indicator.
'in'+'it'+'are'='initare'
'initare' is an anagram of 'INERTIA'.
'due to' acts as a link.
(Other definitions for inertia that I've seen before include "I retain, being without energy" , "Tendency to do nothing or to remain unchanged" , "Slowness to move or act" , "Disinclination to act" , "Lack of movement" .)