The most common and most likely answer to this crossword clue is the 12 letter word BLACKLISTING
I've seen this crossword clue in Financial Times
B
L
A
C
K
L
I
S
T
I
N
G
Buddy explains!

The straight part
We know that "Banning" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case banning = blacklisting.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 BLACKLISTING mean?
BLACKLISTING verb- To place on a blacklist; to mark a person or entity as one to be shunned or banned.
- The act of placing onto a blacklist.