Of course many entered a city (5)
I believe the answer is:
sucre
'a city' is the definition.
(I know that Sucre is a metropolis)
'of course many entered' is the wordplay.
'of course' becomes 'sure' (I've seen this in another clue).
'many' becomes 'c' (C is the Roman numeral for 100).
'entered' indicates putting letters inside.
'sure' going around 'c' is 'SUCRE'.
(Other definitions for sucre that I've seen before include "Ecuadorean currency; sugar (French)" , "Legal capital and former monetary unit of Bolivia" , "sweetener abroad" , "Bolivian city" , "S American capital" .)