Computer scientist Turing (4)
I believe the answer is:
alan
'computer scientist turing' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alan that I've seen before include "Boy's name" , "- Bennett, English dramatist, author" , "- Bennett, English actor, dramatist, writer" , "Sir -- Sugar (The Apprentice)" , "English historian/poet" .)