Principal principle influenced over a clue (9)

I think it could be either:

Which length description are you looking for?:

4,5

core value

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'principal principle influenced' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'over a clue' is the wordplay.
'over a clue' anagrams to 'CORE VALUE'.
However, I am not clear how the anagram is indicated.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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