The Orient Express carries American about (3,4)
I believe the answer is:
far east
'the orient' is the definition.
(I've seen this in another clue)
'express carries american about' is the wordplay.
'express' becomes 'fast' (I've seen this before).
'carries' means one lot of letters goes inside another (inserted letters carried inside).
'american about' becomes 'rea' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'fast' enclosing 'rea' is 'FAR EAST'.
Can you help me to learn more?
(Other definitions for far east that I've seen before include "The Orient" , "Region containing Japan" , "China, Japan and other remote Asian countries" , "remotest Siberia, perhaps" , "distant lands" .)