Writ compelling attendance in court (8)
I believe the answer is:
subpoena
'writ compelling attendance in court' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for subpoena that I've seen before include ""Under penalty" (Latin)" , "Order to appear in court" , "Writ commanding appearance in court" , "Writ ordering someone to attend a court" , "Court-attendance order" .)