Marx hoarding silver in the city (7)
I believe the answer is:
chicago
'city' is the definition.
(Chicago is an example)
'marx hoarding silver' is the wordplay.
'marx' becomes 'chico' (chico marx was a marx brother).
'hoarding' is an insertion indicator.
'silver' becomes 'ag' ('Ag' can be a synonym of 'silver').
'chico' going around 'ag' is 'CHICAGO'.
'in the' is the link.
(Other definitions for chicago that I've seen before include "A Windy City in Illinois" , "American city; musical" , "US city - musical featuring All That Jazz" , "City on Lake Michigan" , "Port on Lake Michigan" .)