Rotating rod (4)
(Other definitions for spindle that I've seen before include "Rod used in spinning" , "Rod on which something rotates" , "Axle rod" , "Rod on which something revolves" , "Rod serving as an axis of rotation" .)
'rotating rod' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for axle that I've seen before include "need of wheeled cart?" , "Rotating rod carrying wheels" , "Wheel support" , "Pin in revolver" , "Bar on which wheels rotate" .)