It goes round up or down (5)
I believe the answer is:
rotor
This clue is a double definition.
'it goes round' is the first definition.
(I've seen this before)
'up or down' is the second definition.
(Other definitions for rotor that I've seen before include "Turning component" , "Helicopter propeller" , "Something mechanical" , "Revolving part of a motor" , "Hub with radiating blades" .)