Keep in Moscow (7)
I believe the answer is:
kremlin
'keep' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'in moscow' is the wordplay.
I cannot really see how this works, but
'in' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for kremlin that I've seen before include "Castle" , "Seat of Russia's government" , "Citadel of a Russian town" , "fortress" , "Moscow's seat of government" .)