Tentative answers may be written in pencil (7)
I believe the answer is:
guesses
'tentative answers' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Perhaps there's a link between them I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for guesses that I've seen before include "Opinions formed with little or no information" , "Forms tentative opinion, thinks likely" , "Hypothesises" , "Conjectures, estimates" , "Conjectures, reckons" .)