Market or exchange (6)
I believe the answer is:
rialto
This clue is a double definition.
'market' is the first definition.
(I've seen this before)
'exchange' is the second definition.
(I've seen this before)
(Other definitions for rialto that I've seen before include "Central area of Venice and suburb of Dublin" , "place of business" , "exchange" , "Island in Venice with famous bridge" , "Area famous for 7 [ABRIDGE]" .)