The most common and most likely answer to this crossword clue is the 10 letter word RANDOMNESS
I've seen this crossword clue in The Guardian
R
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More clues leading to the result RANDOMNESS
Buddy explains!

The straight part
We know that "unpredictability" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unpredictability = randomness.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 RANDOMNESS mean?
RANDOMNESS noun- The property of all possible outcomes being equally likely.
- A type of circumstance or event that is described by a probability distribution.
- A measure of the lack of purpose, logic or objectivity of an event.