Mediocre repetition (2-2)

I believe the answer is:

so-so

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'mediocre' is the definition.
(thesaurus)

I cannot understand how the rest of the clue works.

(Other definitions for so-so that I've seen before include "Informally, only moderately good or well" , "just about adequate" , "Of average quality" , "Only moderately good in repetitive way" , "Barely passable" .)

I've seen this clue in the Evening Standard.

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