Impresario slowly taking in capital (4)
I believe the answer is:
oslo
'capital' is the definition.
(capital of Norway)
'impresario slowly taking' is the wordplay.
'taking' indicates the answer is hidden within the clue (the answer is carried or taken by the clue).
'OSLO' is hidden within 'impresario slowly'.
'in' is the link.
(Other definitions for oslo that I've seen before include "Capital city, called Kristiania until 1924" , "Norwegian chief port" , "Northern capital of Czechoslovakia?" , "Former Christiania" , "It's capital in Anglos London" .)