I can't change. I've become lazy (8)
I believe the answer is:
inactive
'lazy' is the definition.
(thesaurus)
'i can't change i've' is the wordplay.
'change' indicates anagramming the letters.
'cant' with letters rearranged gives 'nact'.
'i'+'nact'+'ive'='INACTIVE'
'become' acts as a link.
(Other definitions for inactive that I've seen before include "Not doing anything, passive" , "Passive or idle" , "Chemically inert" , "Passive, doing nothing" , "Immobile, not working" .)