Copter blade (5)
I believe the answer is:
rotor
'copter blade' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rotor that I've seen before include "Palindromic moving part" , "Palindromic revolving part of machine" , "Eddy" , "The machine part moves in a circle" , "Revolving part of a motor" .)