Carriage taken across America is more crowded maybe (6)
I believe the answer is:
busier
'more crowded maybe' is the definition.
I can't tell whether this definition defines the answer.
'carriage taken across america' is the wordplay.
'carriage' becomes 'bier' (I can't justify this - if you can you should give a lot more credence to this answer).
'taken across' indicates putting letters inside.
'america' becomes 'US' (United States).
'bier' enclosing 'us' is 'BUSIER'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for busier that I've seen before include "Having a great deal more to do" , "More full of activity" , "More fully engaged in work" , "More fully engaged or occupied" , "More active or engaged in work" .)