The most common and most likely answer to this crossword clue is the 7 plus 6 letter word CONTACT LENSES
I've seen this crossword clue in The Sunday Telegraph
C
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N
T
A
C
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L
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S
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More clues leading to the result CONTACT LENSES
Buddy explains!
The straight part
We know that "Visual aids placed just in front of pupils" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case visual aids placed just in front of pupils = contact lenses.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.