Over-repetitive - frightfully! (3-3)

I believe the answer is:

too-too

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'over' is the definition.
(thesaurus)

I don't understand how the remainder of the clue works.

(Other definitions for too-too that I've seen before include "Excessively (colloq.)" , "Excessive" .)

I've seen this clue in the Evening Standard.

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