What does the cryptic crossword clue "Unrealistic hopes of rooks in flight? (7,2,3,3)" mean?

The definition is "Unrealistic hopes / rooks in flight?". The wordplay uses a double definition. Double definition The answer is CASTLES IN THE AIR.

What is the answer to "Unrealistic hopes of rooks in flight? (7,2,3,3)"?

The answer is CASTLES IN THE AIR.

Times Cryptic #28843 | 15 Across | 2024-02-19 flower