The most common and most likely answer to this crossword clue is the 4 plus 4 letter word SELF RULE
S
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Buddy explains!
The straight part
We know that "Sovereignty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sovereignty = self rule.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 SELF RULE mean?
SELF RULE noun- Rule of a group of people by their own leaders as opposed to rule imposed by a foreign government or people.