Young reporter carrying large blunt instrument (4)
I believe the answer is:
club
'blunt instrument' is the definition.
(I've seen this in another clue)
'young reporter carrying large' is the wordplay.
'young reporter' becomes 'cub' (cub can mean a young journalist).
'carrying' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'cub' placed around 'l' is 'CLUB'.
(Other definitions for club that I've seen before include "Eg, wood, brassie" , "See 1" , "Association - bludgeon" , "Weapon for an association" , "In which one could be expecting" .)