Hair arrangement (7)
(Other definitions for topknot that I've seen before include "Chignon: flatfish" , "Fish" , "Bow in hair" , "Crest - tuft of hair" , "Piled up arrangement of hair on the head" .)
'hair arrangement' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for style that I've seen before include "Official title; manner" , "Refinement" , "Superior quality" , "Method; elegance" , "Particular kind, of fashion say" .)