The most common and most likely answer to this crossword clue is the 6 letter word PULLEY
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More clues leading to the result PULLEY
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The straight part
We know that "Simple machine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case simple machine = pulley.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 PULLEY mean?
PULLEY noun- One of the simple machines; a sheave, a wheel with a grooved rim, in which a pulled rope or chain lifts an object (more useful when two or more pulleys are used together, as in a block and tackle arrangement, such that a small force moving through a greater distance can exert a larger force through a smaller distance).
- To raise or lift by means of a pulley.