‘Add vinegar etc to fish' : Jamie's ultimate restaurant rule? (5,4)
I believe the answer is:
dress code
'add vinegar etc' is the definition.
I know nothing about this answer so I can't judge whether this works.
'fish jamie's ultimate restaurant rule?' is the wordplay.
I cannot quite see how this works, but
'fish' could be 'cod' (type of fish) and 'cod' is present in the answer.
'rule?' could be 'r' (abbreviation for rule) and 'r' is found in the answer.
The remaining letters 'desse' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for dress code that I've seen before include "Convention governing clothes to be warn on a particular occasion" , "Stipulated attire" , "Expected standard of attire" , "Guidelines" .)