An excellent main city (7)
I believe the answer is:
capital
This clue is a double definition.
'an excellent' is the first definition.
(I've seen this before)
'main city' is the second definition.
(I've seen this before)
(Other definitions for capital that I've seen before include "Money saved or invested - seat of government" , "Funds" , "A great city - that's fine" , "(Person's) wealth" , "It's jolly good in the great city" .)