Artist captures alien in part one needs to see (6)

I believe the answer is:

retina

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'part one needs to see' is the definition.
I can't judge whether this defines the answer.

'artist captures alien in' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'captures' indicates putting letters inside.
'alien' becomes 'et' (extra terrestrial).
'et'+'in'='etin'
'ra' placed around 'etin' is 'RETINA'.

Can you help me to learn more?

(Other definitions for retina that I've seen before include "Light-sensitive eye lining" , "Retain with part of eye" , "Light-sensitive membrane of the eyeball" , "Sensitive layer in eye" , "Membrane covering the back of the eyeball" .)

I've seen this clue in The Telegraph.

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