I find the definitions a bit murky with this puzzle and I remain stuck on 3 clues: 23 Mob gathered round centre of choky to see child murderer (5) H???D. 13 Sacks, say, for endless waffle (5) R?B?I. 19 Strange surrealists possibly rile this composer (7) S???B?S. If the wordplay could be explained as well, that would be appreciated.