I can't stir, I've become idle (8)
I believe the answer is:
inactive
'idle' is the definition.
(similar in meaning)
'i can't stir i've' is the wordplay.
'stir' is an anagram indicator.
'cant' anagrammed gives 'nact'.
'i'+'nact'+'ive'='INACTIVE'
'become' is the link.
(Other definitions for inactive that I've seen before include "Still" , "Chemically inert" , "Not moving/working" , "Immobile, not working" , "Passive, doing nothing" .)