Machine part that goes up and down (5)

I believe the answer is:

rotor

This clue is a double definition.

'machine part' is the first definition.
(I know that rotor is a machine part)

'that goes up and down' is the second definition.

(Other definitions for rotor that I've seen before include "Eddy" , "Revolving arm in machine" , "Revolving bar" , "Turning component" , "Rotating part of machine" .)

I've seen this clue in the Evening Standard.

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