Codebreaker Turing (4)
I believe the answer is:
alan
'codebreaker turing' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alan that I've seen before include "- Bates, - Bennett" , "-- Ayckbourn, English dramatist" , "English name" , "English historian/poet" , "- Bennett, English actor, dramatist, writer" .)