Couturier resigned in a lather (8)
I believe the answer is:
designer
'couturier' is the definition.
('designer' can be a synonym of 'couturier')
'resigned in a lather' is the wordplay.
'in a lather' indicates anagramming the letters (phrase meaning 'nervous or anxious').
'resigned' anagrammed gives 'DESIGNER'.
(Other definitions for designer that I've seen before include "Fashionable" , "Style creator" , "Producer" , "Originator" , "One who determines the look of something" .)