Writ (8)
I believe the answer is:
subpoena
'writ' is the definition.
(I know that subpoena is a type of writ)
This is all the clue.
(Other definitions for subpoena that I've seen before include "Hearing reminder" , "Write ordering someone to court" , "Writ commanding court attendance" , "calls for appearance in court" , "A summons to attend court case" .)