How a person may be seen to be lying eventually (2,6)

I believe the answer is:

at length

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'eventually' is the definition.
(synonyms)

I don't understand the remainder of the clue.

(Other definitions for at length that I've seen before include "In due course" , "In great detail" , "Finally" , "In exhaustive detail, after a long time" , "Taking a long time like long-winded speech" .)

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

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