Finished with American middlemen and their excessive exploitation (7)
I believe the answer is:
overuse
'excessive exploitation' is the definition.
(using or exploiting excessively)
'finished with american middlemen and' is the wordplay.
I cannot really understand how this works, but
'finished' could be 'over' (over can mean finished or ended) and 'over' is found in the answer.
'american' could be 'us' (United States) and 'us' is found in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'their' is the link.
Can you help me to learn more?
(Other definitions for overuse that I've seen before include "Wear out" , "Excessive utilisation" , "Employ too much" , "Strain" , "Employ excessively" .)