Sheer fabric of silk or rayon (7)
I believe the answer is:
chiffon
'sheer fabric of silk or rayon' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for chiffon that I've seen before include "Fine transparent fabric" , "Fine material" , "Light silk/nylon fabric" , "Sheer silk or rayon fabric" , "Fine (semi)transparent fabric" .)