Dior has endlessly fantastic style (6)
I believe the answer is:
hairdo
'style' is the definition.
(I know that style can be written as hairdo)
'dior has endlessly fantastic' is the wordplay.
'endlessly' means to remove the last letter.
'fantastic' is an anagram indicator.
'dior'+'has'='diorhas'
'diorhas' with its final letter taken away is 'diorha'.
'diorha' with letters rearranged gives 'HAIRDO'.
(Other definitions for hairdo that I've seen before include "Say, crew cut" , "Eg, beehive or mullet" , "Coiffure (colloq.)" , "Pageboy maybe" , "Barnet" .)