Dreadful lawsuit lacking a purpose (9)
I believe the answer is:
direction
'purpose' is the definition.
(thesaurus)
'dreadful lawsuit lacking a' is the wordplay.
'dreadful' becomes 'dire' ('dire' can be a synonym of 'dreadful').
'lawsuit' becomes 'action' ('action' can be a synonym of 'lawsuit').
'lacking' is a deletion indicator.
'action' with 'a' taken away is 'ction'.
'dire'+'ction'='DIRECTION'
(Other definitions for direction that I've seen before include "Course in which something is travelling" , "Trend, tendency" , "The way in which something is moving" , "Tenor" , "Administration" .)