This person's role is to communicate (6)
I believe the answer is:
impart
'communicate' is the definition.
(imparting is a kind of communicating)
'this person's role' is the wordplay.
'this person's' becomes 'im' (this person means the crossword setter themselves).
'role' becomes 'part' ('part' can be a synonym of 'role').
'im'+'part'='IMPART'
'is to' is the link.
(Other definitions for impart that I've seen before include "Share, pass on" , "Divulge, inform" , "Give - relate" , "Armpit (anag)" , "Communicate (info)" .)