Small step into room (5)
I believe the answer is:
space
'room' is the definition.
(I've seen this before)
'small step' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'step' becomes 'pace' (pace is a kind of step).
's'+'pace'='SPACE'
'into' acts as a link.
(Other definitions for space that I've seen before include "Gap; --- Oddity (Bowie)" , "Empty area, may be outer" , "Expanse" , "-- Capsule; -- bar" , "Unfilled region" .)