The others confidently said there's no need to worry (4,7)

I believe the answer is:

rest assured

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'no need to worry' is the definition.
I can't judge whether this defines the answer.

'the others confidently said' is the wordplay.
'the others' becomes 'rest' (I've seen this before).
'confidently said' becomes 'assured' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rest'+'assured'='REST ASSURED'

'there's' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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