Help please with this proms themed Guardian cryptic 26364
6d. I have r-g-d-o- (MUSICAL'S OPENING SNUBBED FOR OLD TIME DANCE)
21a. Sorceress's inner sanctum's in poor condition : this must be anagram. I have c-r-u-s-----
10d. Daily, one with good character, figures on staff : I have T-M-, S-O---U-E
20d. Woman stealing Catholic writer's plot : I have---e-e (Greene??)
Thank you both very much. Rigadoon is new to me and I was way off with 21a. where I was looking for the name of a sorceress. I was also thrown by staff (stave) but I see it now and have changed my "not long now" to "not long ago". Quite tough I thought but thanks again.