Crossword Genius

Keeps up fantasies? (7,2,3,3)

Ross

I believe the answer is:

castles in the air

I'm a little stuck... Click here to teach me more about this clue!

'fantasies?' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'keeps up' is the wordplay.
'keeps' becomes 'castles' (I've seen this before).
'up' becomes 'intheair' (I can't explain this - if you can you should give a lot more credence to this answer).
'castles'+'intheair'='CASTLES IN THE AIR'

Can you help me to learn more?

(Other definitions for castles in the air that I've seen before include "flying fortresses" , "rooks circling overhead" , "dreamy schemes" , "Dreams" , "daydreams" .)

I've seen this clue in the Sydney Morning Herald.
Want a hint initially instead of a full solution? Install my app