The most common and most likely answer to this crossword clue is the 10 letter word ABOUT-TURN
I've seen this crossword clue in The Times
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More clues leading to the result ABOUT-TURN
Buddy explains!

The straight part
We know that "Change of opinion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case change of opinion = about-turn.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 ABOUT-TURN mean?
ABOUT-TURN noun- A turn of 180 degrees, typically in a military formation.
- Total reversal of opinion or attitude.
- To turn 180 degrees, typically in a military formation.