Guinness World Records suffix (3)

I believe the answer is:

est

'guinness world records suffix' is the definition.
(I've seen this in another clue)

This is the entire clue.

(Other definitions for est that I've seen before include "psychological programme" , "self-improvement programme" , "Time Americans adopted" , "Suffix showing superlative" .)

I've seen this clue in the USA Today.

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