Just over 100 connections in urban areas (6)
I believe the answer is:
cities
'urban areas' is the definition.
(city is a kind of urban area)
'just over 100 connections' is the wordplay.
'just over 100' becomes 'ci' (101 in Roman numerals).
'connections' becomes 'ties' (tie is a kind of connection).
'ci'+'ties'='CITIES'
'in' acts as a link.
(Other definitions for cities that I've seen before include "Densely-populated urban areas" , "Large conurbations" , "Dickens novel, 'A Tale of Two ......'" , "Densely populated urban areas" , "Large Urban areas" .)