Annoying situation as big cheese on starter of antipasti isn't finished? Take a mouthful!
I believe the answer is:
headache
'annoying situation' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for headache that I've seen before include "Cause of worry or trouble" , "Major problem" , "nasty problem" , "Worry, trouble (colloq.)" , "trial" .)