Motor shells or bodies (8)
I believe the answer is:
carcases
'bodies' is the definition.
(carcase is a kind of body)
'motor shells' is the wordplay.
'motor' becomes 'car' (I've seen this before).
'shells' becomes 'cases' ('case' can be a synonym of 'shell').
'car'+'cases'='CARCASES'
'or' acts as a link.
(Other definitions for carcases that I've seen before include "Bodies of dead beasts" , "Dead bodies of animals" .)