The most common and most likely answer to this crossword clue is the 11 letter word PREORDAINED
I've seen this crossword clue in The Guardian
P
R
E
O
R
D
A
I
N
E
D
Buddy explains!

The straight part
We know that "decided in advance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decided in advance = preordained.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 PREORDAINED mean?
PREORDAINED verb- To determine the fate of something in advance.
- Determined in advance; predestined