Left in box for journey (6)
I believe the answer is:
flight
'for journey' is the definition.
(flight is a kind of journey)
'left in box' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' indicates putting letters inside.
'box' becomes 'fight' (boxing is a kind of fighting).
'l' put inside 'fight' is 'FLIGHT'.
(Other definitions for flight that I've seen before include "Air force unit; running away" , "The feathers on a dart or arrow" , "Exodus" , "Stairs; escape" , "Series of steps" .)