Very trendy (3,3,4)
I believe the answer is:
all the rage
(Other definitions for all the rage that I've seen before include "Extremely popular" , "Very popular (informal)" , "Very much in fashion" , "in vogue?" , "most desirable now!" .)
I believe the answer is:
all the rage
(Other definitions for all the rage that I've seen before include "Extremely popular" , "Very popular (informal)" , "Very much in fashion" , "in vogue?" , "most desirable now!" .)