Imagine singer can essentially select numbers being performed (4,6)
I believe the answer is:
john lennon
'essentially select numbers being performed' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'imagine singer can' is the wordplay.
I cannot really understand how this works, but
'singer' could be 'lennon' (John Lennon) and 'lennon' is present in the answer.
'can' could be 'john' (slang for toilet) and 'john' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for john lennon that I've seen before include "Imagine his output" , "location of 1 8 [FLYING START] - with 22d" , "Beatle" .)