Large town or populous place (4)
I believe the answer is:
city
I believe this is a double definition.
'large town' is the first definition.
(I've seen this before)
'populous place' is the second definition.
(I've seen this in another clue)
(Other definitions for city that I've seen before include "See 10" , "eg New York" , "Big conurbation" , "Important town" , "Eg, London, Coventry" .)