I tear in to change passivity (7)
I believe the answer is:
inertia
'passivity' is the definition.
(thesaurus)
'i tear in to change' is the wordplay.
'to change' is an anagram indicator.
'tear'+'in'='tearin'
'tearin' anagrammed gives 'nertia'.
'i'+'nertia'='INERTIA'
(Other definitions for inertia that I've seen before include "Stagnating state" , "showing reluctance to move" , "I earn it (anag.)" , "Lethargy" , "Motion (if any) when no external force is applied" .)