Blue flag protects vessel with fish, capsized in sticky substance (6,6)
I believe the answer is:
peanut butter
'blue flag' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'protects vessel with fish capsized in sticky substance' is the wordplay.
I cannot really see how this works, but
'vessel' could be 'butt' (butt is a kind of vessel) and 'butt' is found in the answer.
'substance' could be 'pea' (pea is a kind of substance) and 'pea' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for peanut butter that I've seen before include "something to eat" , "Spread made from groundnuts" , "Golden brown paste" , "Leguminous spread" .)