The most common and most likely answer to this crossword clue is the 10 letter word BITTERNESS
I've seen this crossword clue in The Sunday Telegraph
B
I
T
T
E
R
N
E
S
S
More clues leading to the result BITTERNESS
- Pungency of beer associated with head?
- Acidity of beer with a head on
- Acerbity of a female bird?!
- Acrimony in flier — conclusion often reached by females
- Female marsh bird apparently showing resentment
- Resentment of booming female?
- Resentment of female marsh bird apparently
- Female bird of the heron family apparently shows bad feeling
Buddy explains!

The straight part
We know that "Acrimony" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case acrimony = bitterness.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 BITTERNESS mean?
BITTERNESS noun- The quality of having a bitter taste.
- The quality of feeling bitter; acrimony, resentment.