Newlywed to start bike journey (5)
I believe the answer is:
bride
'newlywed' is the definition.
(bride is a kind of newlywed)
'start bike journey' is the wordplay.
'start' indicates taking the first letters.
'journey' becomes 'ride' (riding is a kind of journeying).
The initial letter of 'bike' is 'b'.
'b'+'ride'='BRIDE'
'to' is the link.
(Other definitions for bride that I've seen before include "presumably honeymoon for me?" , "Groom's mate" , "She's just about to be married" , "Wife of groom" , "one going to church or office?" .)