Latest to arrive, ditching singular old language (5)

I believe the answer is:

latin

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'old language' is the definition.
(Latin is a dead language)

I cannot understand how the rest of the clue works.

(Other definitions for latin that I've seen before include "Cicero's tongue" , "ancient tongue" , "The language of old Rome" , "a quarter of Parisians" , "Parent language of French,Romanian" .)

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