The most common and most likely answer to this crossword clue is the 4 plus 2 plus 8 letter word KEEP IN SUSPENSE
I've seen this crossword clue in Financial Times
K
E
E
P
I
N
S
U
S
P
E
N
S
E
Buddy explains!
The straight part
We know that "to cause uncertainty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to cause uncertainty = keep in suspense.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.