Setter's role is to communicate (6)
I believe the answer is:
impart
'is to communicate' is the definition.
(impart can mean to communicate or pass on)
'setter's role' is the wordplay.
'setter's' becomes 'I'm' (I've seen this in other clues).
'role' becomes 'part' (eg a part or role in a film).
'im'+'part'='IMPART'
(Other definitions for impart that I've seen before include "Transmit" , "Convey information, make known" , "Contribute" , "grant" , "Give - convey" .)