Second in craft (4)
I believe the answer is:
ship
'craft' is the definition.
(I know that craft can be written as ship)
'second in' is the wordplay.
'second' becomes 's' (common abbreviation).
'in' becomes 'hip' (both can mean fashionable).
's'+'hip'='SHIP'
(Other definitions for ship that I've seen before include "craft of 1d [ADVENTURE]" , "Ocean-going vessel" , "Take on" , "See 18" , "eg QE2" .)