The most common and most likely answer to this crossword clue is the 5 letter word DATUM
I've seen this crossword clue in The Times
D
A
T
U
M
More clues leading to the result DATUM
- Piece of information union contributed to barrier
- Looking back, slander getting cheers in fact
- Information corporation supplied to American lawyer
- Lady briefly taking you for a Parisian in fact
- A corporation beyond despicable at first — fact!
- Time short? Then there's little hesitation to provide bit of information
- What boys try to do with girls they fancy, we hear, and that’s a fact
- Piece of information is slander — thanks for breaking it up
- Yes for a Muscovite corporation’s immutable point
- Barrier breached by workers’ alliance — it’s a fact
Buddy explains!

The straight part
We know that "fact" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fact = datum.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does DATUM mean?
DATUM noun- (plural: data) A measurement of something on a scale understood by both the recorder (a person or device) and the reader (another person or device). The scale is arbitrarily defined, such as from 1 to 10 by ones, 1 to 100 by 0.1, or simply true or false, on or off, yes, no, or maybe, etc.
- (plural: data) A fact known from direct observation.
- (plural: data) A premise from which conclusions are drawn.
- (plural: datums) A fixed reference point, or a coordinate system.
- To provide missing data points by using a mathematical model to extrapolate values that are outside the range of a measuring device.