Parade statement that becomes true on April Fool's day (5,4)
I believe the answer is:
march past
'parade statement that becomes true on april fool's day' is the definition.
'march past' can be an answer for 'parade' (type of military parade). I am not sure about the rest of the definition.
'parade statement' is the wordplay.
'parade' becomes 'march' (a ceremonial march).
'statement' becomes 'past' (I can't justify this - if you can you should believe this answer much more).
'march'+'past'='MARCH PAST'
Can you help me to learn more?
(Other definitions for march past that I've seen before include "Companion" , "in previous tax year?" , "Review of forces" , "Army manoeuvre" , "Movement of a body of soldiers being reviewed" .)