Movement in a satellite - it turns (6)
I believe the answer is:
motion
'movement' is the definition.
(synonyms)
'in a satellite it turns' is the wordplay.
'in' means one lot of letters goes inside another.
'a satellite' becomes 'moon' (moon is a kind of satellite).
'turns' shows that the letters should be reversed in order.
'it' backwards is 'ti'.
'moon' going around 'ti' is 'MOTION'.
(Other definitions for motion that I've seen before include "Formal proposal for debate" , "Proposal to be voted on" , "That's debatable" , "Gesture; formal proposal" , "Changing state, moving" .)