Post worker runs daily (12)
I believe the answer is:
newspaperman
'post worker runs' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'daily' is the wordplay.
I cannot really see how this works, but
'daily' could be 'newspaper' (I've seen this before) and 'newspaper' is located in the answer.
The remaining letters 'man' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for newspaperman that I've seen before include "One with editing skill" , "Journalist" , "One of our staff" .)