Flash Gordon's face cloth (5)
I believe the answer is:
glint
'flash' is the definition.
(I know that glint is a type of flash)
'gordon's face cloth' is the wordplay.
'face' indicates taking the first letters.
'cloth' becomes 'lint' (lint is a kind of cloth).
The first letter of 'gordons' is 'g'.
'g'+'lint'='GLINT'
(Other definitions for glint that I've seen before include "A very brief flash of light" , "Glittering flash" , "Flash of light (in the eye?)" , "Momentary flash of light" , "Shine" .)