Compact, tense-free language (4)

I believe the answer is:

erse

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'language' is the definition.
(Erse is an example)

I cannot understand how the remainder of the clue works.

(Other definitions for erse that I've seen before include "Kind of Gaelic for seer" , "Old Celtic language" , "Old language spoken by strange seer" , "Celtic tongue" , "Name sometimes given to languages of the Celts in Ireland and Scotland" .)

I've seen this clue in The Telegraph.

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