No longer liking chair? That's mad (3,4,6)
I believe the answer is:
off ones rocker
'mad' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'no longer liking chair?' is the wordplay.
I cannot quite understand how this works, but
'no' could be 'o' (O resembles 0) and 'o' is located in the answer.
'chair?' could be 'rocker' (rocker is a kind of chair) and 'rocker' is found within the answer.
This explanation may well be incorrect...
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for off ones rocker that I've seen before include "not favouring my dove, > like a fallen Ronnie C?" , "How a seated person might fall" , "Crazy, totally mad" , "Insane" .)