Flat hermetically sealed and injected with foam (6)
I believe the answer is:
lather
'foam' is the definition.
(I know that lather is a type of foam)
'flat hermetically sealed and injected' is the wordplay.
'LATHER' is hidden in amongst the letters.
But, I am unsure how the hidden word is indicated.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for lather that I've seen before include "Frothy bubbles from soap" , "Frothy suds" , "Froth formed by soap and water" , "agitation" , "Froth produced by soap" .)