... design's modified round bottom of Dior clothing (8)
I believe the answer is:
dressing
'clothing' is the definition.
('dress' can be a synonym of 'clothe')
'design's modified round bottom of dior' is the wordplay.
'modified' indicates an anagram.
'round' means one lot of letters goes inside another.
'bottom of' indicates one should take the final letters.
The final letter of 'dior' is 'r'.
'designs' anagrammed gives 'dessing'.
'dessing' placed around 'r' is 'DRESSING'.
(Other definitions for dressing that I've seen before include "Sauce - protection for wound" , "Sauce for salad etc" , "Saucy thing" , "clothing" , "Sauce - alignment - bandage" .)