The most common and most likely answer to this crossword clue is the 8 letter word SARDONIC
I've seen this crossword clue in The Times
S
A
R
D
O
N
I
C
More clues leading to the result SARDONIC
- Conrad is awfully cynical
- Made inroads before cold gets bitter
- Conrad is dreadfully cynical
- Spaniard in Indian dress attracts constant sneering
- Acerbic novel Conrad’s written about Italy
- Cutting as printed describes a radical lecturer
- Pasquale, perhaps, cross-culturally cross-dressing, cold and dry
- Scornful of sound including Queen in publicity
- Nastily said with scorn, heading off?
- Put on dress coats, cold and bitter
Buddy explains!

The straight part
We know that "bitter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bitter = sardonic.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 SARDONIC mean?
SARDONIC adjective- Scornfully mocking or cynical.
- Disdainfully or ironically humorous.