The most common and most likely answer to this crossword clue is the 10 letter word SALMAGUNDI
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The straight part
We know that "a cooked mixed salad" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a cooked mixed salad = salmagundi.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SALMAGUNDI mean?
SALMAGUNDI noun- A food consisting of chopped meat and pickled herring, with oil, vinegar, pepper, and onions.
- Hence, any mixture of various ingredients; an olio or medley; a potpourri; a miscellany.