The most common and most likely answer to this crossword clue is the 10 letter word GOBSTOPPER
I've seen this crossword clue in The Times
G
O
B
S
T
O
P
P
E
R
More clues leading to the result GOBSTOPPER
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 = gobstopper.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 GOBSTOPPER mean?
GOBSTOPPER noun- A type of hard long-lasting candy, usually spherical in shape.