Philosopher's building on the 9 (4)
I believe the answer is:
mill
'philosopher's' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
(Other definitions for mill that I've seen before include "Grind to a powder or dust" , "Flour is produced here" , "Place for grinding flour" , "Fist fight" , "Rob < works" .)