Philosopher grinding here (4)
I believe the answer is:
mill
This might be a double definition.
'philosopher' is the first definition.
(John Stuart Mill)
'grinding here' is the second definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
Can you help me to learn more?
(Other definitions for mill that I've seen before include "Where work is a grind" , "Building in which grain is ground to flour" , "Advocate of the utilitarian" , "Move around in a confused mass" , "works on > race" .)