The most common and most likely answer to this crossword clue is the 11 letter word HIT-OR-MISS
I've seen this crossword clue in The Guardian
H
I
T
-
O
R
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M
I
S
S
More clues leading to the result HIT-OR-MISS
Buddy explains!
The straight part
We know that "Unpredictable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unpredictable = hit-or-miss.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 HIT-OR-MISS mean?
HIT-OR-MISS adjective- Inconsistent, unpredictable, erratic; sometimes succeeding and sometimes failing.