23d) Pianist's energy rising with party number (5) O???N

[susanwilton]

Third letter may be D, so I thought may be the pianist Ogdon, but don't understand the energy part of the clue!

[mike11111]

Reverse of GO at the start

[squarebear]

Go is energy (rising is OG)
party could be a "do"
and n for number

[susanwilton]

Thank you both, now it makes more sense! It was from the BBC Music Magazine.