Umpire’s call assumed to be reversed (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 cannot tell whether this works.
'assumed to be reversed' is the wordplay.
'assumed' becomes 'put on' (synonyms).
'to be reversed' says the letters should be written backwards.
'puton' back-to-front is 'NOT UP'.
Can you help me to learn more?
(Other definitions for not up that I've seen before include "call in court" , "still in bed" , "with tennis call" .)