Sort of mistake that could make one late (5)

I believe the answer is:

fatal

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'late' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for fatal that I've seen before include "Causing death, say accident" , "Bringing death" , "Mortal" , "Pernicious" , "Death-dealing" .)

I've seen this clue in The Globe and Mail.

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