Degrade Mass in Church with end of Latin (7)
I believe the answer is:
cheapen
'degrade' is the definition.
('cheapen' can be a synonym of 'degrade')
'mass in church with end of latin' is the wordplay.
'mass' becomes 'heap' ('heap' can be a synonym of 'mass'**).
'in' means one lot of letters goes inside another.
'church' becomes 'ce' (abbreviation for Church of England).
'with' means one lot of letters go next to another.
'end of' indicates one should take the final letters.
The final letter of 'latin' is 'n'.
'heap' placed into 'ce' is 'cheape'.
'cheape'+'n'='CHEAPEN'
(Other definitions for cheapen that I've seen before include "Reduce the price of" , "Cut" , "Degrade (something)" , "Tried" , "lower" .)