Nothing terribly grand that is material (8)
I believe the answer is:
Here is my best explanation:
'material' is the definition.
(organdie is a kind of material)
'nothing terribly grand that is' is the subsidiary indication.
'nothing' becomes 'o' (looks like zero - 0).
'terribly' is an anagram indicator.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'grand' with letters rearranged gives 'rgand'.
(Other definitions for organdie that I've seen before include "Material", "Fine stiffened translucent fabric", "Cotton muslin", "Cotton fabric used for dresses", "Badly ignored a fine cotton muslin", "Orange I'd changed for fine muslin", "Fine cotton muslin", "I raged on about the fabric", "A stiffened muslin; I groaned (anag.)" and "Translucent cotton fabric, usually stiffened".)