Wheel originally steering powered missile (8)
I believe the answer is:
sprocket
'wheel' is the definition.
(sprocket wheel is a kind of wheel)
'originally steering powered missile' is the wordplay.
'originally' says to take the initial letters.
'missile' becomes 'rocket' (I've seen this in another clue).
The initial letters of 'steering powered' is 'sp'.
'sp'+'rocket'='SPROCKET'
(Other definitions for sprocket that I've seen before include "Toothed wheel that interlocks with a chain" , "Part of a wheel" , "Thin wheel with teeth driven by a chain" , "It helps to drive" , "Series of teeth on wheel engaging with chain" .)