Shepard in space
I believe the answer is:
alan
'shepard in space' 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 "Messrs Ladd and Dukes" , "-- Turing, English computer scientist" , "Boy's name" , "-- Turing, mathematician" , "Boy" .)