The most common and most likely answer to this crossword clue is the 3 plus 3 plus 2 plus 4 letter word THE DIE IS CAST
I've seen this crossword clue in The Guardian
T
H
E
D
I
E
I
S
C
A
S
T
Buddy explains!
The straight part
We know that "it’s too late to change" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s too late to change = the die is cast.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.