The usual, of course (3)
I believe the answer is:
par
This clue might be a double definition.
'the usual' is the first definition.
(par is an average golf score)
'course' is the second definition.
I know that 'course' relates to this answer. I also know that both the answer and definition are singular nouns
'of' is the link.
Can you help me to learn more?
(Other definitions for par that I've seen before include "Usual score at golf" , "Norm" , "Accepted standard" , "Accepted level" , "Face value; equal standing" .)