The most common and most likely answer to this crossword clue is the 11 letter word KNOW-IT-ALL
K
N
O
W
-
I
T
-
A
L
L
More clues leading to the result KNOW-IT-ALL
Buddy explains!

The straight part
We know that "well informed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case well informed = know-it-all.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.
Crossword Answer definitions
KNOW-IT-ALL noun- Someone who claims to be knowledgeable or an expert in something, obnoxiously dismissing the opinions, advice, suggestions, etc. of others.