Many long dresses incorporate such material (5)
I believe the answer is:
nylon
'material' is the definition.
(nylon is a kind of material)
'many long dresses incorporate' is the wordplay.
'incorporate' says the answer is hidden in the clue (I've seen 'incorporates' mean this).
'NYLON' is hidden in the letters of 'many long dresses'.
'such' is the link.
(Other definitions for nylon that I've seen before include "Fibre of polymeric amides" , "Hosiery material" , "Tights material" , "Artificial cloth" , "Unaccompanied part song" .)