Tripe's eaten, and sticky stuff in coating of yolk (12)
I believe the answer is:
gobbledygook
'tripe's' is the definition.
(both can mean nonsense)
'eaten and sticky stuff in coating of yolk' is the wordplay.
'eaten' becomes 'gobbled' (gobbling is a kind of eating).
'and' is a charade indicator (letters next to each other).
'sticky stuff' becomes 'goo' (goo is a sticky substance).
'in' is an insertion indicator.
'coating of' means to remove the middle letters (only the letters that coat the word remain).
'yolk' with its centre removed is 'yk'.
'goo' inserted within 'yk' is 'ygook'.
'gobbled'+'ygook'='GOBBLEDYGOOK'
(Other definitions for gobbledygook that I've seen before include "Nonsense!" , "Officialese" , "bunk?" , "Meaningless language" .)