The most common and most likely answer to this crossword clue is the 13 letter word UNMENTIONABLE
I've seen this crossword clue in The Daily Telegraph
U
N
M
E
N
T
I
O
N
A
B
L
E
More clues leading to the result UNMENTIONABLE
Buddy explains!
The straight part
We know that "Scandalous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case scandalous = unmentionable.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 UNMENTIONABLE mean?
UNMENTIONABLE noun- Something not to be discussed in polite society.
- Not mentionable