Review on April 1st? (5,4)
I believe the answer is:
march past
'review' is the definition.
(I have seen 'Review of forces' mean 'march past' so perhaps 'review' could also mean 'march past')
'april 1st?' is the wordplay.
I cannot really understand how this works, but
'1st?' could be 'st' and 'st' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'on' is the link.
Can you help me to learn more?
(Other definitions for march past that I've seen before include "Parade before a saluting base" , "ceremonial parade" , "Movement of a body of soldiers being reviewed" , "Companion" , "Military parade" .)