Stopped solving case with journalist (6)
I believe the answer is:
ceased
'stopped' is the definition.
('cease' can be a synonym of 'stop')
'solving case with journalist' is the wordplay.
'solving' indicates an anagram (anagrams are puzzles).
'with' is a charade indicator (letters next to each other).
'journalist' becomes 'ed' (short for editor).
'case' is an anagram of 'ceas'.
'ceas'+'ed'='CEASED'
(Other definitions for ceased that I've seen before include "Finished" , "Concluded" , "Stopped, desisted" , "Stopped or discontinued" , "Terminated" .)