Immobility (7)
I believe the answer is:
inertia
'immobility' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for inertia that I've seen before include "showing reluctance to move" , "Disinclination to respond" , "Slowness to take action, state of laziness" , "Passivity" , "Resistance to change" .)