A little world in space (3)
I believe the answer is:
This might be a double definition.
'a little world' is the first definition.
The definition suggests a singular noun which matches the answer.
'space' is the second definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'in' is the link.
Can you help me to learn more?
(Another definition for mir that I've seen is " Russian space station".)