As sealed in silence? (4)
I believe the answer is:
lips
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for lips that I've seen before include "Fleshy folds of tissue" , "Edges of the mouth" , "Olivia's two, 'indifferent red' (T. Night)" , "Brims, rims" , "margins" .)