Clue: Those keeping note of regnal number? (3,6,4)
Answer: TWO LITTLE BOYS
Explanation: Those keeping note of regnal number? (3,6,4)
I have absolutely no idea what this is about – it's the title of the song made famous by Rolf Harris, so perhaps "number" is the definition, but otherwise…*Thanks to Rullytully and JuneG for the explanation: the TWO LITTLE BOYS are Reg and Al, who are "keeping" a "note" (n) in Reg(n)Al