Enthusiasm from travel around America? Tons (5)

I believe the answer is:

gusto

I'm a little stuck... Click here to teach me more about this clue!

'enthusiasm' is the definition.
(I know that gusto is a type of enthusiasm)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for gusto that I've seen before include "Great enjoyment in doing something" , "exhilaration" , "Zest, zeal" , "Relish - zest" , "Exuberant enjoyment" .)

I've seen this clue in The Times and The Sunday Times.

Want a hint initially instead of a full solution? Install my app