That's the truth (4)

I think it could be either:

Which length description are you looking for?:

fact

'that's the truth' is the definition.
(true facts)

This is the entire clue.

(Other definitions for fact that I've seen before include "Certain thing" , "Item of truth" , "Something known to be true" , "Actuality" , "True item; reality" .)

I've seen this clue in The Wall Street Journal.

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