The most common and most likely answer to this crossword clue is the 7 letter word ELIXIRS
I've seen this crossword clue in The Times
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Buddy explains!

The straight part
We know that "sovereign remedies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sovereign remedies = elixirs.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 ELIXIRS mean?
ELIXIRS noun- A liquid which converts lead to gold.
- A substance or liquid which is believed to cure all ills and give eternal life.
- (by extension) The alleged cure for all ailments; cure-all, panacea.
- A sweet flavored liquid (usually containing a small amount of alcohol) used in compounding medicines to be taken by mouth in order to mask an unpleasant taste.