The most common and most likely answer to this crossword clue is the 7 letter word MALTOSE
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More clues leading to the result MALTOSE
Buddy explains!

The straight part
We know that "sugar" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sugar = maltose.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 MALTOSE mean?
MALTOSE noun- A disaccharide, C12H22O11 formed from the digestion of starch by amylase; is converted to glucose by maltase; it is an isomer of trehalose