The Four Tops in elegant tuxedos, unique in fashion designer’s case? (4)
I believe the answer is:
etui
'case?' is the definition.
(case for needlework equipment)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for etui that I've seen before include "Sewer's case" , "Case for holding sewing articles" , "The Case of the Seamstress" , "Ornamental ladies' bag for small articles" , "Tiny ladies' bag" .)