Step on board for vacant accommodation (6)
I believe the answer is:
spaces
'for vacant accommodation' is the definition.
I can't judge whether this definition defines the answer.
'step on board' is the wordplay.
'step' becomes 'pace' (pace is a kind of step).
'on' is an insertion indicator.
'board' becomes 'ss' (I've seen this in other clues).
'pace' going into 'ss' is 'SPACES'.
Can you help me to learn more?
(Other definitions for spaces that I've seen before include "Blank areas" , "cleared areas" , "distances" , "boxes" , "Gaps" .)