Cryptic crossword clue
Piece of glass cut to press on specimen, primarily? 9

The most common and most likely answer to this crossword clue is the 9 letter word COVERSLIP

I've seen this crossword clue in The Guardian
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Buddy explains!

The straight part
We know that "Piece of glass" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case piece of glass = coverslip.
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 COVERSLIP mean?

COVERSLIP noun
  1. A thin glass plate used to cover samples mounted on a microscope slide.
COVERSLIP verb
  1. To cover (a sample) with a coverslip.

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