Herald regularly spurned flashing light on computer screen (9)
I believe the answer is:
precursor
'herald' is the definition.
(I know that herald can be written as precursor)
'regularly spurned flashing light on computer screen' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'flashing light on computer screen' becomes 'cursor' (I can't justify this - if you can you should believe this answer much more).
The alternating letters of 'spurned' are 'pre'.
'pre'+'cursor'='PRECURSOR'
Can you help me to learn more?
(Other definitions for precursor that I've seen before include "Man coming before me" , "harbinger of what is to follow" , "One coming before" , "Forerunner, predecessor" , "Herald" .)