Timetable for Mass (9)
I believe the answer is:
programme
'timetable' is the definition.
(I know that programme is a type of timetable)
'for mass' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'mass' becomes 'gramme' (unit of mass).
'pro'+'gramme'='PROGRAMME'
(Other definitions for programme that I've seen before include "Schedule of events" , "Menu of events" , "List of events" , "Radio or television show" , "Radio or TV broadcast" .)