Main line luggage (5)
I believe the answer is:
trunk
This clue is a double definition.
'main line' is the first definition.
(thesaurus)
'luggage' is the second definition.
(I know that trunk is a type of luggage)
(Other definitions for trunk that I've seen before include "Large luggage case" , "Main body - chest" , "What's packed in" , "Main stem of tree" , "Large luggage box" .)