The most common and most likely answer to this crossword clue is the 5 letter word BOMBE
I've seen this crossword clue in Independent
B
O
M
B
E
More clues leading to the result BOMBE
- Dessert was a failure, lacking finishing touch
- Old boy about to get Palace's recognition? That's sweet
- Start on brandy then ring gong for dessert
- Dessert was a failure, lacking depth
- Bowled over by honour – it’s sweet
- Dessert that may go off, we’re told
- Utter failure, Jamie’s last dessert
- Sweet smell given award
- Dessert, pineapple, last from tree
- 2/3rd of Bombay has English dessert
Buddy explains!

The straight part
We know that "sweet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sweet = bombe.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 BOMBE mean?
BOMBE noun- A dessert made from ice cream frozen in a (generally spherical or hemispherical) mold.
- (chiefly in German cooking) A small, cylindrical or spherical chocolate-covered confection. (Compare truffle.)
- An electromechanical device used in early cryptanalysis.