Rejected measure of cloth containing silicon material (5)
I believe the answer is:
lisle
'material' is the definition.
(I know that lisle is a type of material)
'rejected measure of cloth containing silicon' is the wordplay.
'rejected' says the letters should be written in reverse.
'measure of cloth' becomes 'ell' (historical unit of measurement for fabric).
'containing' is an insertion indicator.
'silicon' becomes 'Si' (Si is the chemical symbol for silicon).
'ell' enclosing 'si' is 'elsil'.
'elsil' reversed gives 'LISLE'.
(Other definitions for lisle that I've seen before include "(Fabric woven with) a fine cotton thread" , "Fine cotton thread used in stockings" , "Strong tightly twisted cotton thread" , "Maker of hose" , "Pedestrianised city" .)