Cook made a new fillet (6)
I believe the answer is:
anadem
'fillet' is the definition.
(wreath for the head)
'cook made a new' is the wordplay.
'cook' indicates anagramming the letters.
'new' becomes 'n'.
'made'+'a'+'n'='madean'
'madean' with letters rearranged gives 'ANADEM'.
(Other definitions for anadem that I've seen before include "Chaplet" , "Garland for head of maenad" , "Fillet" , "Wreath" .)