Dawn, perhaps, for this train ticket? (3,6)
I believe the answer is:
day return
'dawn perhaps for this train ticket?' is the definition.
'day return' can be an answer for 'train ticket?' (day return is a type of train ticket). I am not sure about the remainder of the definition.
'train ticket?' is the wordplay.
'train' becomes 'day' (I am not sure about this - if you are sure you should believe this answer much more).
'ticket?' becomes 'return' (return ticket is a kind of ticket).
'day'+'return'='DAY-RETURN'
(Other definitions for day return that I've seen before include "Type of ticket" , "cheap ticket" , "There-and-back short-term ticket" .)