Serious grant? (5)
I believe the answer is:
grave
This clue might be a double definition.
'serious' is the first definition.
(both can mean solemn)
'grant?' is the second definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's a link between them I don't understand?
(Other definitions for grave that I've seen before include "place one might take their rest" , "Grim-faced" , "Burial place is serious" , "Grievous, serious" , "Serious in a crypt" .)