Time to study utilitarianism, but it's a grind (9)
I believe the answer is:
treadmill
'it's a grind' is the definition.
(both can mean a tedious job)
'time to study utilitarianism' is the wordplay.
'time' becomes 't' (abbreviation).
'to study utilitarianism' becomes 'readMill' (John Stuart Mill wrote about utilitarianism).
't'+'readmill'='TREADMILL'
'but' is the link.
(Other definitions for treadmill that I've seen before include "Wheel turned by walking animals or people" , "Routine drudgery -- exercise machine" , "Dull routine" , "Routine activity" , "Sportspeople utilise this" .)