Jolly good city like London (7)
I believe the answer is:
capital
This clue is a triple definition!
'jolly good' is the first definition.
(I've seen this in another clue)
'city' is the second definition.
(capital is a kind of city)
'like' is a link.
'london' is the third definition.
(I've seen this before)
(Other definitions for capital that I've seen before include "Metropolis" , "Topping" , "A big letter, or a big city" , "city such as London" , "Cardiff, say" .)