US city or country, overpopulated originally (7)
I believe the answer is:
orlando
'us city' is the definition.
(I've seen this before)
'or country overpopulated originally' is the wordplay.
'country' becomes 'land' (synonyms).
'originally' indicates taking the first letters.
The first letter of 'overpopulated' is 'o'.
'or'+'land'+'o'='ORLANDO'
(Other definitions for orlando that I've seen before include "Bloom in film" , "Romantic lead in "As You Like It" - the Marmalade Cat" , "Florida resort -- Virginia Woolf novel" , "Disney World location" , "2016 Invictus Games city - Virginia Woolf novel" .)