Helicopter part (5)
I believe the answer is:
rotor
'helicopter part' is the definition.
('rotor' is part of 'helicopter')
This is the entire clue.
(Other definitions for rotor that I've seen before include "Turning part of a mechanism" , "Mechanical part that revolves, an acronym" , "Revolving arm in machine" , "Revolving blade (as on helicopter)" , "Mechanical turning part" .)