Had deteriorated and was taking dope? (4,2,3)
I believe the answer is:
gone to pot
'had deteriorated and' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'taking dope?' is the wordplay.
I cannot quite understand how this works, but
'taking' could be 'on' (eg one taking drugs is 'on' drugs) and 'on' is found within the answer.
'dope?' could be 'pot' (both can informally mean cannabis) and 'pot' is located in the answer.
This may be the basis of clue (or it may be nonsense).
'was' is the link.
Can you help me to learn more?
(Another definition for gone to pot that I've seen is " Totally deteriorated".)