Bankers from Poughkeepsie, in their chopper, coming to peak (4)
I believe the answer is:
apex
'to peak' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for apex that I've seen before include "reasonable fare" , "Point or summit" , "The highest point of something" , "Uppermost point" , "Summit - pinnacle" .)