Case of cruelty — way medic may treat one (4)
I believe the answer is:
cyst
'medic may treat one' is the definition.
I can't tell whether this definition defines the answer.
'case of cruelty way' is the wordplay.
'case of' means to remove the middle letters (outsides of).
'way' becomes 'st' (abbreviation for street).
'cruelty' with its centre removed is 'cy'.
'cy'+'st'='CYST'
Can you help me to learn more?
(Other definitions for cyst that I've seen before include "Abnormal body sac containing fluid" , "Bladder" , "Thin-walled cavity containing liquid" , "Bag of fluid" , "Fluid-filled sac (med.)" .)