Dress code subject (6)
I believe the answer is:
attire
'dress code subject' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for attire that I've seen before include "I treat badly the dress." , "Clothing - tear it (anag)" , "Formal clothing" , "'Dress, garb (6)'" , "Fine/formal clothes" .)