Fashion new dome (4)
I believe the answer is:
mode
'fashion' is the definition.
(I know that fashion can be written as mode)
'new dome' is the wordplay.
'new' indicates anagramming the letters.
'dome' is an anagram of 'MODE'.
(Other definitions for mode that I've seen before include "Style (of clothes, etc)" , "Trend" , "Form or style" , "Mistake" , "Way of doing something" .)