Woman crossing over platform, say (4)
I believe the answer is:
shoe
'platform say' is the definition.
(platform is a kind of shoe)
'woman crossing over' is the wordplay.
'woman' becomes 'she' ().
'crossing' indicates putting letters inside (to cross can mean to go over or around).
'over' becomes 'o' (cricket abbreviation).
'she' enclosing 'o' is 'SHOE'.
(Other definitions for shoe that I've seen before include "Slip-on or lace-up?" , "Maybe casual" , "Camera mounting" , "Oxford, perhaps" , "Oxford, say" .)