The most common and most likely answer to this crossword clue is the 10 letter word VACILLATED
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Buddy explains!

The straight part
We know that "Was unsure" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case was unsure = vacillated.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 VACILLATED mean?
VACILLATED verb- To sway unsteadily from one side to the other; oscillate.
- To swing indecisively from one course of action or opinion to another.