“Capital” is “big”, see (4)
I believe the answer is:
oslo
'capital' is the definition.
(Oslo is an example)
'big see' is the wordplay.
'big' becomes 'os'.
'see' becomes 'lo' (archaic word meaning 'look!').
'os'+'lo'='OSLO'
'is' is the link.
(Other definitions for oslo that I've seen before include "European capital, known until 1924 as Christiania" , "Norwegian city, formerly Kristiania" , "European capital city (found in Czechoslovakia!)" , "Norwegian capital" , "Location" .)