One month ended in ceremonial parade (5,4)
I believe the answer is:
march past
'ceremonial parade' is the definition.
(I've seen this before)
'one month ended' is the wordplay.
'one month' becomes 'march' (March is an example).
'ended' becomes 'past' (I've seen this before).
'march'+'past'='MARCH PAST'
'in' acts as a link.
(Other definitions for march past that I've seen before include "Movement of a body of soldiers being reviewed" , "ceremonial parade" , "Review of forces" , "Military parade" , "Army manoeuvre" .)