The most common and most likely answer to this crossword clue is the 6 plus 2 letter word YOU’RE ON
I've seen this crossword clue in The Guardian
Y
O
U
â
€
™
R
E
O
N
More clues leading to the result YOU’RE ON
Buddy explains!
The straight part
We know that "Agreed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case agreed = you’re on.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.