Sash worn, mostly decorated (7)
I believe the answer is:
baldric
'sash' is the definition.
(historical type of belt)
'worn mostly decorated' is the wordplay.
'worn' becomes 'bald' (bald can mean worn away).
'mostly' means to remove the last letter.
'decorated' becomes 'rich' (rich can mean decorated or fancy).
'rich' with its last letter removed is 'ric'.
'bald'+'ric'='BALDRIC'
(Other definitions for baldric that I've seen before include "is under one's belt" , "Sword-belt" , "Carrier for weapon" , "Strapping swordsman carried" , "Sword belt" .)