Some steps placed outside an upper window (8)
I believe the answer is:
fanlight
'upper window' is the definition.
(I've seen this before)
'some steps placed outside an' is the wordplay.
'some steps' becomes 'flight' (I've seen this before).
'placed outside' indicates putting letters inside.
'flight' going around 'an' is 'FANLIGHT'.
(Other definitions for fanlight that I've seen before include "elevated aperture" , "opening over the door" , "Rectangular window over a door" , "Thin flag (anag.)" , "upper window?" .)