The most common and most likely answer to this crossword clue is the 7 letter word PUPPETS
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More clues leading to the result PUPPETS
Buddy explains!

The straight part
We know that "Marionettes" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case marionettes = puppets.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 PUPPETS mean?
PUPPETS noun- Any small model of a person or animal able to be moved by strings or rods, or in the form of a glove.
- A person, country, etc, controlled by another.
- A poppet; a small image in the human form; a doll.
- The upright support for the bearing of the spindle in a lathe.