Act as go-between (6)
I believe the answer is:
liaise
'act as 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 "Communicate with for mutual benefit" , "Mediate" , "Ast as go-between" , "Form a link (with)" , "Keep in touch to co-operate on something" .)