The most common and most likely answer to this crossword clue is the 8 letter word TRUNNION
I've seen this crossword clue in Independent
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Buddy explains!
The straight part
We know that "rotating pin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rotating pin = trunnion.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 TRUNNION mean?
TRUNNION noun- One of the short stubby bearings on either side of a cannon; a gudgeon.
- A similar rotational bearing comprising a rotating arc or ring sliding in the groove of a stationary arc, used in machinery to allow a workpiece to be moved relative to a fixed tool.
- A similar rotational bearing used in automotive suspensions.