Review on 1st of April (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')
'1st of april' is the wordplay.
I cannot really see how this works, but
'1st' could be 'st' and 'st' is located in the answer.
This explanation may well be incorrect...
'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" , "Review of forces" , "Companion" , "Army manoeuvre" .)