Reality about to get inverted in newspaper (4)
I believe the answer is:
fact
'reality' is the definition.
(fact is a kind of reality)
'about to get inverted in newspaper' is the wordplay.
'about' becomes 'ca' (short for circa).
'to get inverted' says the letters should be written backwards.
'in' indicates putting letters inside.
'newspaper' becomes 'FT' (Financial Times newspaper).
'ca' backwards is 'ac'.
'ac' going within 'ft' is 'FACT'.
(Other definitions for fact that I've seen before include "True statement" , "given" , "Certain thing" , "Something known to be true" , "Indisputable thing" .)