Thin material in newspaper article is unknown (7)
I believe the answer is:
organza
'thin material' is the definition.
(I've seen this before)
'in newspaper article is unknown' is the wordplay.
'in' is an insertion indicator.
'newspaper' becomes 'organ' (I've seen this before**).
'article' becomes 'a' (indefinite article).
'is unknown' becomes 'z' (algebra).
'organ'+'a'='organa'
'organa' going around 'z' is 'ORGANZA'.
(Other definitions for organza that I've seen before include "Stuff" , "dress material" , "Transparent silk material" , "Transparent silky material" , "Thin stiff natural or synthetic fabric" .)