Well-heeled American should follow the Duke of Milan (10)
I believe the answer is:
prosperous
'well-heeled' is the definition.
(synonyms)
'american should follow the duke of milan' is the wordplay.
I cannot really understand how this works, but
'american' could be 'us' (abbreviation for United States) and 'us' is present in the answer.
'duke' could be 'prospero' (I've seen this before) and 'prospero' is found in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for prosperous that I've seen before include "Well-to-do" , "Affluent" , "Wealthy" , "thriving" , "Doing well" .)