Unhealthy group transgressed 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 can't explain this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'see' becomes 'rome' (the Holy See or See of Rome is home to the pope).
'synd'+'rome'='SYNDROME'
'transgressed we' acts as a link.
This may not be correct. 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 "Set of linked symptoms" , "Characteristic pattern of symptoms" , "set of opinions" , "Signs of disorder" , "collection of twenty four's [SYMPTOM]" .)