Broad sash — old one worn by bishop (3)
I believe the answer is:
'broad sash' is the definition.
(I've seen this before)
'old one worn by bishop' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'one' becomes 'i' (Roman numeral**).
'worn by' is an insertion indicator (I've seen this in other clues).
'bishop' becomes 'b' (abbreviation used in chess).
'oi' going around 'b' is 'OBI'.
(Other definitions for obi that I've seen before include "Martial arts sash" , "exotic waistband" , "Form of witchcraft" , "belt" , "Kimono accessory" .)