Reluctance to move (7)
I believe the answer is:
inertia
'reluctance to move' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for inertia that I've seen before include "'Sluggishness, indolence (7)'" , "Tendency to inactivity" , "Slowness to act, lassitude" , "lack of action" , "Lack of movement" .)