Viral content contains detailed class film (8)
I believe the answer is:
membrane
'film' is the definition.
(I've seen this before)
'viral content contains detailed class' is the wordplay.
'viral content' becomes 'meme' (as in an internet meme).
'contains' indicates putting letters inside.
'detailed' means to remove the last letter (the word must be end-less or 'de-tailed').
'class' becomes 'brand'.
'brand' with its final letter taken away is 'bran'.
'meme' enclosing 'bran' is 'MEMBRANE'.
(Other definitions for membrane that I've seen before include "Thin sheet surrounding body parts" , "Thin pliable sheet of body tissue" , "Thin pliable sheet of material" , "Layer surrounding cells" , "Thin skin-like tissue lining organs" .)