This too shall pass (3)
I believe the answer is:
fad
'this too shall pass' 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, all the rage (3)'" , "Caprice" , "Temporary vogue or craze" , "Passionate interest" , "A craze, usually passing" .)