All this, to me, is incomprehensible (5)

I believe the answer is:

greek

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'all this to me is incomprehensible' is the definition.
The definition suggests a singular noun which matches the answer.

This is all the clue.

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(Other definitions for greek that I've seen before include "Mediterranean native" , "One from Salonika" , "(Unknown?) European language" , "Hellene" , "Supposedly unknown language?" .)

I've seen this clue in the Evening Standard.

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