Hot trend (3)
I believe the answer is:
fad
'hot 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 "Craze; idiosyncrasy" , "Passionate interest" , "Short-lived craze" , "A craze or current vogue" , "A passing fancy or fashion" .)