The pound note is about to make a comeback, John (5)
I believe the answer is:
elton
'john' is the definition.
(musician Elton John)
'the pound note is about to make a comeback' is the wordplay.
'the pound' becomes 'L' (the pound sign is based on an L).
'is about' means one lot of letters goes inside another.
'to make a comeback' says the letters should be written backwards (I've seen 'making a comeback' mean this).
'l' placed into 'note' is 'notle'.
'notle' reversed gives 'ELTON'.
(Other definitions for elton that I've seen before include "Let on he's John, the singer" , "Ben --; -- John" , "One John" , "..... Jonn (musician)" , "- John, British singer" .)