Starts to disembark arriving into station platform (4)
I believe the answer is:
dais
'platform' is the definition.
(dais is a kind of platform)
'starts to disembark arriving into station' is the wordplay.
'starts to' indicates taking the first letters.
The first letters of 'disembark arriving into station' is 'DAIS'.
(Other definitions for dais that I've seen before include "support for speaker" , "Said to be a low platform" , "Speaker's raised platform" , "device to give some an uplift at conference?" , "Platform, rostrum" .)