Newsman set about new objective (3)
I believe the answer is:
end
'objective' is the definition.
(both can mean a purpose)
'newsman set about new' is the wordplay.
'newsman' becomes 'ed' (short for editor).
'set about' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'ed' going around 'n' is 'END'.
(Other definitions for end that I've seen before include "'Conclusion, finale (3)'" , "Goal; destruction" , "Closure" , "Conclusion or goal" , "Concluding purpose" .)