Not well after having most of the rich cake and a pancake (8)
I believe the answer is:
tortilla
'pancake' is the definition.
(I know that tortilla is a type of tortilla)
'not well after having most of the rich cake and a' is the wordplay.
'not well' becomes 'ill' ('ill' is the opposite to 'well').
'after having' says to put letters next to each other.
'most of' means to remove the last letter.
'the rich cake' becomes 'torte' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'torte' with its last letter removed is 'tort'.
'ill' after 'tort' is 'tortill'.
'tortill'+'a'='TORTILLA'
(Other definitions for tortilla that I've seen before include "One; military grouping" , "Spanish omelette" , "Mexican corn-meal pancake" , "Littoral (anag.)" , "Mexican flatbread" .)