Change... open up, seeing European city (10)
I believe the answer is:
copenhagen
'european city' is the definition.
(capital of Denmark)
'change open up' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'change'+'open'='changeopen'
'changeopen' with letters rearranged gives 'COPENHAGEN'.
'seeing' is the link.
(Other definitions for copenhagen that I've seen before include "European capital" , "below Wellington" , "Duke of 21's horse at Waterloo -- capital city" , "Danish capital" , "Capital - Wellington's warhorse" .)