The most common and most likely answer to this crossword clue is the 17 letter word CLOUD-CUCKOO-LAND
I've seen this crossword clue in The Times
C
L
O
U
D
-
C
U
C
K
O
O
-
L
A
N
D
More clues leading to the result CLOUD-CUCKOO-LAND
- Mad about noisy estate outside fantasy realm
- Bananas in dull bag coming to fantasy realm
- Fantastic place to come down to follow obscure bird
- Crazy about noisy estate outside fantasy realm
- Dilapidated condo? Could caulk make it Aristophanes's paradise?
- Deciphering incomplete code could unlock a utopian realm
Buddy explains!
The straight part
We know that "fantasy realm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fantasy realm = cloud-cuckoo-land.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.
What does CLOUD-CUCKOO-LAND mean?
CLOUD-CUCKOO-LAND noun- An imaginary place where silly or unrealistic people metaphorically reside.