Fanciful (9)
There are a few possibilities for this:
'fanciful' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for whimsical that I've seen before include "Mischievous" , "Capricious" , "odd" , "Quaintly fantastic" , "Delicately playful" .)
(Other definitions for airy-fairy that I've seen before include "Unrealistic - fanciful" , "Fanciful, not based on reality" , "Lightweight" , "Fanciful and impractical like breezy sprite" , "Fanciful or impractical for breezy elf" .)
'fanciful' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for unreal that I've seen before include "Lacking in substance" , "Lacking material form" , "Phantasmagorical" , "Not genuine" , "Illusory, not actual" .)
'fanciful' is the definition.
(I know that fanciful can be written as notional)
This is the entire clue.
(Other definitions for notional that I've seen before include "Existing as theory, not existing in reality" , "Assumed to be correct for particular purpose, say estimate" , "Theoretic" , "Hypothetical, assumed to be correct" , "Unreal" .)
(Other definitions for illusory that I've seen before include "dreamed up" , "false" , "Not real, imagined" , "Deceptive" , "Unreal, fanciful" .)