Sheet material (5)
I believe the answer is:
linen
'sheet material' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for linen that I've seen before include "Fabric, originally just spun flax" , "Tablecloth material" , "Sheets, tablecloth etc." , "Sheets, pillowcases etc" , "bedsheets?" .)