A sphere lacking reality (5,5)

I believe the answer is:

dream world

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'a sphere' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?

'lacking reality' is the wordplay.
'lacking' becomes 'dream' (I am not sure about this - if you are sure you should believe this answer much more).
'reality' becomes 'world' (synonyms).
'dream'+'world'='DREAM-WORLD'

Can you help me to learn more?

(Other definitions for dream world that I've seen before include "Fool's paradise" , "Imaginary place" .)

I've seen this clue in The Globe and Mail.

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