Missing second support at home area for light detector (6)

I believe the answer is:

retina

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(Other definitions for retina that I've seen before include "Retain with part of eye" , "Membrane covering the back of the eyeball" , "Tear in (anag) - part of the eye" , "Sensitive part of eye" , "Back surface of eye" .)

I've seen this clue in The Hindu.

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