The most common and most likely answer to this crossword clue is the 6 letter word TAPPET
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More clues leading to the result TAPPET
Buddy explains!
The straight part
We know that "part of engine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of engine = tappet.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 TAPPET mean?
TAPPET noun- A lever or projection which is moved by some other piece, as a cam, or intended to tap or touch something else, in order to produce change or regulate motion.