No way presumably to greet the day (4,5)
I believe the answer is:
good night
'no' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'way presumably to greet the day' is the wordplay.
I cannot quite understand how this works, but
'way' could be 'n' (Compass direction - North) and 'n' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'day' could be 'd' (abbreviation for day) and 'd' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for good night that I've seen before include "last message" , "Final greeting" .)