Mental impression of Jemima Goldsmith (5)

I believe the answer is:

imago

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'mental impression' is the definition.
'imago' can be an answer for 'impression' (thesaurus). I am unsure of the 'mental' bit.

'of jemima goldsmith' is the wordplay.
'of' indicates a hidden word.
'IMAGO' is hidden in the letters of 'jemima goldsmith'.

Can you help me to learn more?

(Other definitions for imago that I've seen before include "latest development in cricket?" , "That's as far as a butterfly can go" , "Adult insect after metamorphosis" , "idealised figure" , "Last state of insect life" .)

I've seen this clue in The Independent.

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