The most common and most likely answer to this crossword clue is the 8 letter word LINOTYPE
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The straight part
We know that "printing machine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case printing machine = linotype.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 LINOTYPE mean?
LINOTYPE noun- A form of typesetting machine in which a complete line of characters is set at once.
- The slug produced by such a machine, or matter composed in such lines.
- To prepare (printed matter) using a linotype machine.