The most common and most likely answer to this crossword clue is the 8 letter word MEDIATOR
I've seen this crossword clue in The Daily Telegraph
M
E
D
I
A
T
O
R
More clues leading to the result MEDIATOR
- One seeking agreement riot made mad
- Mark article penned by journalist who seeks to resolve problem?
- Male journalist welcoming a go-between
- Spiritualists fell for peacemaker
- Go-between made trio resolved
- Contemplative individual sacrificing some time for one seeking compromise
- Go-between to admire when resolution has been established
- Arbitrator made it complex, in other words
- Press and TV nonsense upset referee
- ‘The Go-Between‘: novel to admire or ‘arid tome’?
Buddy explains!

The straight part
We know that "go-between" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case go-between = mediator.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 MEDIATOR mean?
MEDIATOR noun- One who negotiates between parties seeking mutual agreement.
- A chemical substance transmitting information to a targeted cell.