The most common and most likely answer to this crossword clue is the 8 letter word ACRIMONY
I've seen this crossword clue in Financial Times
A
C
R
I
M
O
N
Y
More clues leading to the result ACRIMONY
- The writer’s taken in by a sidekick — bitterness results
- Bitterness of American crook, regularly missing bounty
- Goliath is overwhelmed by a friend’s belligerence
- Resentment at settlement, getting credit for pound
- A bloody year, with no small ill-feeling
- Arrives before Poins is overwhelmed by companion’s bitterness
- This person’s probing a friend’s resentment
- Lilac rim on yam’s inside reveals bitterness
- Bitterness from a baseless misdemeanour over New Year
- I’m probing a mate’s bitterness
Buddy explains!

The straight part
We know that "Resentment" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case resentment = acrimony.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 ACRIMONY mean?
ACRIMONY noun- A sharp and bitter hatred.