Hip again (5)
I believe the answer is:
retro
'hip again' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for retro that I've seen before include "reminding us of the past" , "Describes the style of an earlier time, in short" , "suggestive of past" , "Style derived from the past" , "Consciously old style" .)