One at the receiving end (9)
I believe the answer is:
addressee
This clue could be a double definition.
'one' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'the receiving end' is the second definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'at' is the link.
Can you help me to learn more?
(Other definitions for addressee that I've seen before include "Recipient of mail" , "The one to whom the message is sent" , "Recipient of post" , "One named on summons" , "One sent letter" .)