A big box for the old bus (5)
I believe the answer is:
crate
This could be a double definition.
'a big box' is the first definition.
'crate' can be an answer for 'box' (I've seen this before). I'm not certain of the 'a big' bit.
'the old bus' is the second definition.
'crate' can be an answer for 'bus' (thesaurus). I am not certain of the 'the old' bit.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for crate that I've seen before include "Wooden box" , "old banger" , "Dilapidated vehicle" , "Packing-case made of wooden slats" , "Old car" .)