Dreams hide a secret when you look behind the surface (5)

I believe the answer is:

ideas

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

'dreams' is the definition.
The answer and definition can be both related to thinking as well as being plural nouns.
Maybe they are linked in a way I don't understand?

'hide a secret when you look behind the surface' is the wordplay.
'IDEAS' is hidden within the letters.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for ideas that I've seen before include "plans" , "Fancies" , "Thoughts from Sadie" , "Thoughts, concepts" , "Thoughts, perceptions" .)

I've seen this clue in The Independent.

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