Flash Gordon's original material (5)
I believe the answer is:
glint
'flash' is the definition.
(I know that glint is a type of flash)
'gordon's original material' is the wordplay.
'original' indicates taking the first letters.
'material' becomes 'lint' (lint is a kind of material).
The initial letter of 'gordons' is 'g'.
'g'+'lint'='GLINT'
(Other definitions for glint that I've seen before include "Spark" , "Brief indication" , "Small flash of light" , "Reflect" , "Momentary flash of light" .)