Astronaut Shepard (4)
I believe the answer is:
alan
'astronaut shepard' 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 "Messrs Ladd and Dukes" , "- Ayckbourn, English playwright" , "- Bennett, English dramatist, author" , "- Bennett, English actor, dramatist, writer" , "Boy" .)