Clue: Having lately joined a certain choir? Absolutely (4)
Answer: DEAD
Explanation: Definition: Having lately joined a certain choir
Double definition – reference to the phrase "joined the choir eternal", as used in the sketch. I presume the expression didn't originate there, but googling only seems to find Dead Parrot references. *As Eileen points out, it's actually "choir invisible" – see comments for a link to the source of this.