Capital and income principally invested in new casino (7)
I believe the answer is:
nicosia
'capital' is the definition.
(Nicosia is an example)
'income principally invested in new casino' is the wordplay.
'principally' suggests taking the first letters.
'invested in' indicates putting letters inside.
'new' indicates an anagram.
The first letter of 'income' is 'i'.
'casino' with letters rearranged gives 'nicosa'.
'i' put into 'nicosa' is 'NICOSIA'.
'and' is the link.
(Other definitions for nicosia that I've seen before include "Mediterranean capital" , "Casino I visit in Cyprus" , "It's capital in Cyprus (7)" , "Largest city on Cyprus" , "Casino I used in Cyprus" .)