Additions to window over sink? Not something I can comment on perhaps (5,4)

I believe the answer is:

blind spot

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But I can't explain it at all! Could you help me understand?

(Other definitions for blind spot that I've seen before include "where one cannot see" , "source of misunderstanding?" , "Area where understanding is lacking or one is unsighted" , "Unseen area of road" , "Hazard for driver" .)

I've seen this clue in The Times.

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