The most common and most likely answer to this crossword clue is the 10 plus 1 letter word MARMALADE} –
I've seen this crossword clue in The Daily Telegraph
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Buddy explains!
The straight part
We know that "Preserve" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case preserve = marmalade} –.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 MARMALADE} – mean?
MARMALADE} – noun- Citrus fruit variant of jam but distinguished by being made slightly bitter by the addition of the peel and by partial caramelisation during manufacture. Most commonly made with Seville oranges, and usually qualified by the name of the fruit when made with other types of fruit.
- To spread marmalade on.