Revolutionary screen showing "Umpire's call" (3,2)
I believe the answer is:
not up
'umpire's call' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'revolutionary screen' is the wordplay.
'revolutionary' says the letters should be written in reverse (letters revolve around).
'screen' becomes 'puton' (I am not sure about this - if you are sure you should believe this answer much more).
'puton' written backwards gives 'NOT UP'.
'showing' is the link.
Can you help me to learn more?
(Other definitions for not up that I've seen before include "still in bed" , "call in court" , "with tennis call" .)