Motor part (3)
I believe the answer is:
cam
'motor part' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cam that I've seen before include "running into Great Ouse?" , "Bump on a shaft for pushing another shaft" , "running through university city?" , "academic stream" , "Projection on a rotating shaft in contact with another part" .)