Fashionable once again (5)
I believe the answer is:
retro
'fashionable once again' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for retro that I've seen before include "Slangy adjective for harking back to the past" , "Imitative of an older style" , "Associated with the past" , "Describes the style of an earlier time, in short" , "Reliving the past" .)