Act as a go-between (6)
I believe the answer is:
liaise
'act as a go-between' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for liaise that I've seen before include "Intercommunicate" , "Cooperate on a matter of mutual concern" , "Collaborate" , "Keep in touche with" , "Work together" .)