Except for the additional decoration (3)
I believe the answer is:
bar
'except for' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bar that I've seen before include "Barristers - band" , "Bank, shoal" , "Ingot" , "Counter; pressure unit" , "Sandbank; prohibit" .)