The most common and most likely answer to this crossword clue is the 10 letter word PROSCRIBED
I've seen this crossword clue in The Times
P
R
O
S
C
R
I
B
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D
More clues leading to the result PROSCRIBED
Buddy explains!

The straight part
We know that "Banned" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case banned = proscribed.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 PROSCRIBED mean?
PROSCRIBED verb- To forbid or prohibit.
- To denounce.
- To banish or exclude.