The lethargy I retain however moved (7)
I believe the answer is:
inertia
'the lethargy' is the definition.
(both can mean a lack of movement)
'i retain however moved' is the wordplay.
'i retain' can be anagrammed to 'INERTIA'.
Though, I am not clear how this is indicated.
Can you help me to learn more?
(Other definitions for inertia that I've seen before include "'Sluggishness, indolence (7)'" , "Lethargy" , "I retain, being without energy" , "Slowness to act, lack of strength" , "showing reluctance to move" .)