The most common and most likely answer to this crossword clue is the 8 letter word RECANTED
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result RECANTED
Buddy explains!

The straight part
We know that "forswore beliefs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case forswore beliefs = recanted.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 RECANTED mean?
RECANTED verb- To withdraw or repudiate a statement or opinion formerly expressed, especially formally and publicly.