[Just like that!] (4)
(Another definition for bam that I've seen is " hoax".)
(Other definitions for bang that I've seen before include "Report - something the hairdresser did?" , "Fringe - report" , "Completely modern" , "Sudden noise; fringe" , "Explosion; hair fringe" .)
(Other definitions for in a flash that I've seen before include "Where American detected electricity" , "How lightning appears" , "pictures may be taken" , "Instantly, straightaway" , "Almost instantly" .)