Way up (or down) (5)
I believe the answer is:
stair
'way up or down' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stair that I've seen before include "Support on which to step" , "One step in a series" , "something of a case" , "one on the way up" , "One step of a flight" .)