The most common and most likely answer to this crossword clue is the 10 letter word ABSOLUTISM
I've seen this crossword clue in Financial Times
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The straight part
We know that "Autocratic rule" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case autocratic rule = absolutism.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 ABSOLUTISM mean?
ABSOLUTISM noun- Doctrine of preordination; doctrine of absolute decrees; doctrine that God acts in an absolute manner.
- The principles or practice of absolute or arbitrary government; despotism.
- Belief in a metaphysical absolute; belief in Absolute.
- Positiveness; the state of being absolute.
- The characteristic of being absolute in nature or scope; absoluteness.