Since changes, Cuba's capital is picturesque (6)
I believe the answer is:
scenic
'picturesque' is the definition.
(thesaurus)
'since changes cuba's capital' is the wordplay.
'changes' indicates anagramming the letters.
'capital' indicates taking the first letters.
The initial letter of 'cuba' is 'c'.
'since' is an anagram of 'sceni'.
'sceni'+'c'='SCENIC'
'is' is the link.
(Other definitions for scenic that I've seen before include "Having attractive views like some routes" , "Of route, having pleasent views" , "Having nice views along the route" , "Like beautiful landscape" , "worth viewing" .)