Short-lived trend (3)
I believe the answer is:
fad
'short-lived trend' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fad that I've seen before include "A passing fashion or craze" , "A craze or current vogue" , "Short-lived craze" , "Caprice" , "Personal whim" .)