The most common and most likely answer to this crossword clue is the 14 letter word OPHTHALMOSCOPE
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Buddy explains!
The straight part
We know that "one to look into your eyes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one to look into your eyes = ophthalmoscope.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does OPHTHALMOSCOPE mean?
OPHTHALMOSCOPE noun- An instrument for examining the interior of the eye (that is, for ophthalmoscopy).