I can’t move: I have become sluggish (8)
I believe the answer is:
Here is my best explanation:
'sluggish' is the definition.
('inactive' can be similar in meaning to 'sluggish')
'i can't move i have' is the wordplay.
'move' is an anagram indicator.
'i have' becomes 'ive'.
'cant' is an anagram of 'nact'.
'become' acts as a link.
(Other definitions for inactive that I've seen before include "Immobile, not working", "Passive, doing nothing", "Resting", "Quiescent", "Not moving/working", "Lifeless", "Having no effect", "Lethargic", "Unoccupied" and "sluggish".)