End of album, one with Lennon, not stereo (4)
I believe the answer is:
mono
'not stereo' is the definition.
(I've seen this in another clue)
'end of album one with lennon' is the wordplay.
'end of' suggests the final letters.
'one with' means one lot of letters go next to another.
'lennon' becomes 'ono' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The last letter of 'album' is 'm'.
'm'+'ono'='MONO'
Can you help me to learn more?
(Other definitions for mono that I've seen before include "Single-channel sound" , "Single-speaker sound" , "Not stereo" , "Transmitting over one channel" .)