I fantasise about everything under the sun (10)
I believe the answer is:
daydreamer
'sun' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'i fantasise about everything under' is the wordplay.
I cannot really understand how this works, but
'i' could be 'me' and 'me' is found within the answer.
'about' could be 'rea' (I've seen this in other clues) and 'rea' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'the' acts as a link.
Can you help me to learn more?
(Other definitions for daydreamer that I've seen before include "one in a brown study" , "Fantasist" , "One in a reverie" , "Wishful thinker" , "One letting their mind wander" .)