Material to make Gordian knot undone in the end (8)
I believe the answer is:
organdie
'material' is the definition.
(organdie is a kind of material)
'gordian knot undone in the end' is the wordplay.
'knot' is an anagram indicator (I've seen 'knotted' mean this).
'in the end' says to take the final letters.
The final letter of 'undone' is 'e'.
'gordian' with letters rearranged gives 'organdi'.
'organdi'+'e'='ORGANDIE'
'to make' is the link.
(Other definitions for organdie that I've seen before include "Fine material" , "Oddly ignored a fine cotton muslin" , "Cotton fabric used for dresses" , "Fine slightly stiff cotton dress fabric" , "Orange I'd changed for fine muslin" .)