The most common and most likely answer to this crossword clue is the 9 letter word UNANIMOUS
I've seen this crossword clue in Financial Times
U
N
A
N
I
M
O
U
S
More clues leading to the result UNANIMOUS
- As one man is on, two union leaders off
- USA union forced to adopt first of mandates in accord
- First off: Uncle Sam union to be wound up, everyone agreed
- Contrary granny from Finland posh, everyone agrees
- In complete agreement with peacekeepers over containing hostility? Just the opposite
- Everyone agrees to turn in an unforgettable start at sumo wrestling
- United, in sum, on a move?
- UN article given Finnish backing without dissent
- All agreed to distribution of a union sum
- As one promoter of peace oversees hostility, nothing must interrupt
Buddy explains!

The straight part
We know that "everyone agreed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case everyone agreed = unanimous.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 UNANIMOUS mean?
UNANIMOUS adjective- Based on unanimity, assent or agreement.
- Sharing the same views or opinions, and being in harmony or accord.