The most common and most likely answer to this crossword clue is the 5 plus 4 letter word SUGAR LOAF
I've seen this crossword clue in The Daily Telegraph
S
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Buddy explains!
The straight part
We know that "used in sweet cake" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case used in sweet cake = sugar loaf.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 SUGAR LOAF mean?
SUGAR LOAF noun- A block of refined sugar, usually in the form of a truncated cone, in which form it was traditionally exported from the Caribbean and Brazil from the 17th century to the 19th century.
- A hat shaped like a sugar-loaf.