Exclude group's first report (4)
I believe the answer is:
bang
'report' is the definition.
(report can mean a loud noise)
'exclude group's first' is the wordplay.
'exclude' becomes 'ban' (I've seen this in other clues).
'group's first' becomes 'g' (1st letter of 'group').
'ban'+'g'='BANG'
(Other definitions for bang that I've seen before include "Sound of explosion" , "Straight fringe of hair" , "Hairstyle" , "precisely" , "Completely modern" .)