Unfortunately, I retain a lack of movement (7)
I believe the answer is:
inertia
'a lack of movement' is the definition.
(I've seen this before)
'unfortunately i retain' is the wordplay.
'unfortunately' is an anagram indicator.
'i'+'retain'='iretain'
'iretain' anagrammed gives 'INERTIA'.
(Other definitions for inertia that I've seen before include "Immobility" , "Motionlessness" , "Resistance to change" , "showing reluctance to move" , "'Sluggishness, indolence (7)'" .)