Top European is able to maintain a large missile launching site (4,9)
I believe the answer is:
cape canaveral
'missile launching site' is the definition.
I can't judge whether this defines the answer.
'top european is able to maintain a large' is the wordplay.
'top european' becomes 'cape' (I can't justify this - if you can you should believe this answer much more).
'is able to' becomes 'can' (if you can do something you are able to do it).
'maintain' becomes 'aver' (averring is a kind of maintaining).
'large' becomes 'L' (eg in clothes sizes).
'cape'+'can'+'aver'+'a'+'l'='CAPE CANAVERAL'
Can you help me to learn more?
(Other definitions for cape canaveral that I've seen before include "US space launch site" , "US space launch centre" , "Florida space flight centre" , "space reached from here" .)