Ruin church parade (5)
I believe the answer is:
march
'parade' is the definition.
('march' can be a synonym of 'parade')
'ruin church' is the wordplay.
'ruin' becomes 'mar' (I've seen this before**).
'church' becomes 'ch' (common abbreviation).
'mar'+'ch'='MARCH'
(Other definitions for march that I've seen before include "Stride; month" , "Walk in a resolute manner" , "Parade" , "Military walk; month" , "Walk formally in step with others" .)