Fox News screening nothing positive (7)
I believe the answer is:
nonplus
'fox' is the definition.
('nonplus' can be a synonym of 'fox')
'news screening nothing positive' is the wordplay.
'news' becomes 'nn' (I've seen this in other clues).
'screening' is an insertion indicator (I've seen this in other clues).
'nothing' becomes 'o' (looks like zero - 0).
'positive' becomes 'plus' ('plus' can be similar in meaning to 'positive').
'nn' going around 'o' is 'non'.
'non'+'plus'='NONPLUS'
(Other definitions for nonplus that I've seen before include "Cause dismay" , "Perplex, confound" , "Confound, bewilder" , "Throw into confusion" , "Floor" .)