One who issues invitations to many people (4)
I believe the answer is:
host
'one who issues invitations to many people' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for host that I've seen before include "Crowd-entertainer" , "One entertains guests" , "great many!" , "Entertainer of guests" , "One receiving guests" .)