Capital from island invested in new casino (7)
I believe the answer is:
nicosia
'capital' is the definition.
(capital of Cyprus)
'island invested in new casino' is the wordplay.
'island' becomes 'i' (geographical abbreviation).
'invested in' indicates putting letters inside.
'new' indicates an anagram.
'casino' anagrammed gives 'nicosa'.
'i' going within 'nicosa' is 'NICOSIA'.
'from' is the link.
(Other definitions for nicosia that I've seen before include "Mediterranean city" , "European Union's most southerly capital" , "Divided Cypriot city" , "Casino I visit in Cyprus" , "It's capital in Cyprus (7)" .)