Promises Caesar: 'Sun's to rise' (10)

I believe the answer is:

assurances

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'promises' is the definition.
(assurance is a kind of promise)

'caesar sun's to rise' is the wordplay.
'caesar sun's' anagrams to 'ASSURANCES'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Another definition for assurances that I've seen is " Promises".)

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

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