Perhaps pop star Dido cold at heart (4)

I believe the answer is:

idol

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

'perhaps pop star' is the definition.

'dido cold at heart' is the wordplay.
'dido' becomes 'id' (I can't explain this - if you can you should believe this answer much more).
'at heart' means to look at the middle letters.
The middle letters of 'cold' are 'ol'.
'id'+'ol'='IDOL'

Can you help me to learn more?

(Other definitions for idol that I've seen before include "Admired figure" , "Image of a god (not icon)" , "Hero, star" , "As before, fake" , "Billy" .)

I've seen this clue in The Everyman puzzle in The Observer.

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