Calmly suggest removing contents to get sac (4)
I believe the answer is:
cyst
'sac' is the definition.
(I know that cyst is a type of sac)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cyst that I've seen before include "Fluid-filled sac (med.)" , "Small growth" , "Abnormal body sac containing fluid" , "Benign growth" , "Bladder" .)