The most common and most likely answer to this crossword clue is the 8 letter word ICECREAM
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More clues leading to the result ICECREAM
Buddy explains!

The straight part
We know that "dessert" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dessert = icecream.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 ICECREAM mean?
ICECREAM noun- A dessert made from frozen sweetened cream or a similar substance, usually flavoured.
- A portion of ice cream on a stick, in a cup or in a wafer cone.