Unhealthy group erred, from what we hear and see (8)
I believe the answer is:
syndrome
'unhealthy group' is the definition.
(group of medical symptoms)
'hear and see' is the wordplay.
'hear' becomes 'synd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'see' becomes 'rome' (the Holy See or See of Rome is home to the pope).
'synd'+'rome'='SYNDROME'
'erred from what we' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for syndrome that I've seen before include "Group of symptoms indicating a disease" , "Group of linked symptoms" , "Characteristic group of symptoms" , "Combination of symptoms" , "Signs of disorder" .)