The most common and most likely answer to this crossword clue is the 7 plus 2 plus 3 plus 3 letter word CASTLES IN THE AIR
I've seen this crossword clue in The Daily Telegraph
C
A
S
T
L
E
S
I
N
T
H
E
A
I
R
More clues leading to the result CASTLES IN THE AIR
- Flying Fortresses just daydreams?
- Unrealistic hopes of seeing rooks flying?
- Keeps up unrealistic plans
- Intricate hassle having to alter unrealistic plans
- Former minister inherits a messy set of unrealistic plans
- One can get lost in these non-realistic fantasies essentially getting built
- Hates recitals arranged to include popular imaginative items
Buddy explains!
The straight part
We know that "unrealistic plans" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unrealistic plans = castles in the air.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.