The most common and most likely answer to this crossword clue is the 12 letter word BAD-TEMPERED
I've seen this crossword clue in Independent
B
A
D
-
T
E
M
P
E
R
E
D
More clues leading to the result BAD-TEMPERED
Buddy explains!
The straight part
We know that "Nasty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nasty = bad-tempered.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 BAD-TEMPERED mean?
BAD-TEMPERED adjective- Of or pertaining to bad temper; showing anger easily or customarily.