Movement of car rested back of skull (7)
I believe the answer is:
cranial
'of skull' is the definition.
(I've seen this before)
'movement of car rested back' is the wordplay.
'movement of' indicates anagramming the letters (I've seen 'movement' mean this (letters move around)).
'rested' becomes 'lain' ('lie' can be a synonym of 'rest').
'back' shows that the letters should be reversed in order.
'lain' in reverse letter order is 'nial'.
'car' anagrammed gives 'cra'.
'cra'+'nial'='CRANIAL'
(Another definition for cranial that I've seen is " Of the skull".)