"____ True Thing" (3)
'true thing' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fact that I've seen before include "copyright protection agency?" , "Piece of information known to be true" , "Certain thing" , "An indisputable truth" , "Verifiable truth" .)
(Other definitions for one that I've seen before include "Unit" , "United" , "Figure" , "This is singular" , "Single and undivided" .)