Everyone in wide thoroughfare in financial centre (4,6)
I believe the answer is:
wall street
'financial centre' is the definition.
(I've seen this before)
'everyone in wide thoroughfare' is the wordplay.
'everyone' becomes 'all' (I've seen this before).
'in' means one lot of letters goes inside another.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'thoroughfare' becomes 'street' (street is a kind of thoroughfare).
'w'+'street'='wstreet'
'all' inserted into 'wstreet' is 'WALL STREET'.
'in' acts as a link.
(Other definitions for wall street that I've seen before include "US financial area" , "Film" , "Financial district" , "New York finance centre" , "business centre" .)