Writing lie about material (7)
I believe the answer is:
textile
'material' is the definition.
(I know that material can be written as textile)
'writing lie about' is the wordplay.
'writing' becomes 'text' (text is a kind of writing).
'about' indicates an anagram.
'lie' with letters rearranged gives 'ile'.
'text'+'ile'='TEXTILE'
(Other definitions for textile that I've seen before include "'Fabric, material (7)'" , "Woven material" , "Woven cloth" , "Woven or machine-knitted fabric" , "Cloth made by weaving or knitting" .)