Yellow strip lined with new sort of material (7)
I believe the answer is:
organza
'sort of material' is the definition.
(I know that organza is a type of cloth)
'yellow strip lined with new' is the wordplay.
'yellow' becomes 'or' (heraldic term).
'strip' becomes 'gaza' (I've seen this before).
'lined with' is an insertion indicator (as in being filled or lined with something).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'gaza' enclosing 'n' is 'ganza'.
'or'+'ganza'='ORGANZA'
(Other definitions for organza that I've seen before include "Thin stiff natural or synthetic fabric" , "Thin stiff dress fabric" , "Silk (or silk-like) fabric" , "Silky fabric" , "Transparent silky material" .)