What's carried about in box? (7)
I believe the answer is:
freight
'box?' is the definition.
(thesaurus)
'what's carried about' is the wordplay.
'what's' becomes 'fight' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'carried' means one lot of letters goes inside another.
'about' becomes 're' (regarding).
'fight' enclosing 're' is 'FREIGHT'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for freight that I've seen before include "Something carried" , "Goods carries by large vehicle" , "Commercial transport" , "Goods in transit" , "Cargo, goods transported" .)