Derby date changed for sleeping partner? (5,4)

I believe the answer is:

teddy bear

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'sleeping partner?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'derby date changed' is the wordplay.
'changed' is an anagram indicator.
'derby'+'date'='derbydate'
'derbydate' is an anagram of 'TEDDY BEAR'.

'for' acts as a link.

Can you help me to learn more?

(Other definitions for teddy bear that I've seen before include "Soft toy" , "cling to this for comfort?" , "Cuddly ursine" , "Popular cuddly toy" , "Child's toy, musically in picnic" .)

I've seen this clue in The Sun and The Times.

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