One's problem is mental perception (6)

I believe the answer is:

noesis

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'mental perception' is the definition.
'noesis' can be an answer for 'perception' (thesaurus). I am not sure about the 'mental' bit.

'one's problem is' is the wordplay.
'problem' indicates an anagram.
'ones' anagrammed gives 'noes'.
'noes'+'is'='NOESIS'

Can you help me to learn more?

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

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