Complaint made by topless Americans who deliver letters on time (7)
I believe the answer is:
ailment
'complaint' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ailment that I've seen before include "Minor illness" , "Malady" , "Complaint, affliction" , "Physical disorder" , "I lament (anag.)" .)