Say what you think is right — at heart famous serial needs to change (8)

I believe the answer is:

moralise

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'say what you think is right' is the definition.
I can't tell whether this definition defines the answer.

'heart famous serial needs to change' is the wordplay.
'heart' says to take the centre.
'needs to change' is an anagram indicator.
The centre of 'famous' is 'mo'.
'serial' is an anagram of 'ralise'.
'mo'+'ralise'='MORALISE'

'at' acts as a link.

Can you help me to learn more?

(Another definition for moralise that I've seen is " Preach".)

I've seen this clue in The Times.

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