Gaps in small steps (6)
I believe the answer is:
spaces
'gaps' is the definition.
(I've seen this before)
'small steps' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'steps' becomes 'paces' (pace is a kind of step).
's'+'paces'='SPACES'
'in' acts as a link.
(Other definitions for spaces that I've seen before include "Open areas" , "Empty areas" , "boxes" , "distances" , "cleared areas" .)