habeas corpus, for one (4)
I believe the answer is:
writ
'habeas corpus for one' is the definition.
(I know that habeas corpus is a type of writ)
This is all the clue.
(Other definitions for writ that I've seen before include "Formal legal command" , "official order" , "Warrant, court order" , "Subpoena" , "court paper" .)