Flying rooks in one's daydreams (7,2,3,3)
I believe the answer is:
castles in the air
This clue could be a double definition.
'flying rooks' is the first definition.
(I've seen this before)
'one's daydreams' is the second definition.
'castles in the air' can be an answer for 'daydreams' (I've seen this in another clue). I'm unsure of the 'one's' bit.
'in' is the link.
Can you help me to learn more?
(Other definitions for castles in the air that I've seen before include "rooks circling overhead" , "Unrealistic hopes" , "dreamy schemes" , "flying fortresses" , "Dreams" .)