go-between
noun /ˈɡəʊ bɪtwiːn/
  /ˈɡəʊ bɪtwiːn/
[countable, uncountable]- a person who takes messages between one person or group and another
- to act as (a) go-between
 - A number of local church leaders have acted as go-betweens with the paramilitaries.