The most common and most likely answer to this crossword clue is the 10 letter word REVELATORY
I've seen this crossword clue in The Guardian
R
E
V
E
L
A
T
O
R
Y
More clues leading to the result REVELATORY
Buddy explains!

The straight part
We know that "informative" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case informative = revelatory.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 REVELATORY mean?
REVELATORY adjective- Of, pertaining to, or in the nature of a revelation
- Prophetic (especially of doom); apocalyptic