City ___ (place for a population sign) (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
limits
(Other definitions for limits that I've seen before include "Boundaries, points beyond which something cannot continue" , "Frontiers" , "Bounds beyond which one cannot go" , "'Boundaries, demarcation lines (6)'" , "Curtails" .)