A mere craze that starts fading (3)

I believe the answer is:

fad

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'a mere craze' is the definition.
'fad' can be an answer for 'craze' (synonyms). I am not certain of the 'a mere' bit.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for fad that I've seen before include "Short-lived craze" , "Craze; idiosyncrasy" , "A passing fancy or fashion" , "A passing fashion or craze" , "A craze or current vogue" .)

I've seen this clue in the Evening Standard.

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