Professor's job security (6)
I believe the answer is:
tenure
'professor's job security' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tenure that I've seen before include "The holding of land or property" , "Term for which to hold a position" , "Way of holding" , "The holding of office or land" , "Tenancy" .)