Part of a cycle (5)
I believe the answer is:
pedal
I believe this is a double definition.
'part' is the first definition.
(I have seen 'part of organ' mean 'pedal' so perhaps 'part' could also mean 'pedal')
'cycle' is the second definition.
(pedal can mean to cycle a bicycle)
'of a' is the link.
(Other definitions for pedal that I've seen before include "cause a revolution in cycling?" , "work with press from Oxford?" , "sustained note" , "One of two a cyclist needs" , "part of organ" .)