One of those fancy ideas (5)

I believe the answer is:

dream

I'm a little stuck... Click here to teach me more about this clue!

'fancy ideas' is the definition.
'dream' can be an answer for 'fancy' (both can mean a fantasy). I am not certain of the 'ideas' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for dream that I've seen before include "Armed (anag)" , "Sleeper's vision" , "Nocturnal vision" , "Fantasy; imagine" , "Switch off" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.