The most common and most likely answer to this crossword clue is the 8 letter word SULTANAS
I've seen this crossword clue in The Times
S
U
L
T
A
N
A
S
More clues leading to the result SULTANAS
Buddy explains!

The straight part
We know that "Sweet little thing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sweet little thing = sultanas.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 SULTANAS mean?
SULTANAS noun- A pale yellow raisin made from a seedless grape.
- A female sultan or wife or mistress of a sultan.
- A female ruler of a sultanate.
- A kind of viol.
- An old form of necklace.