The most common and most likely answer to this crossword clue is the 8 letter word MOLASSES
I've seen this crossword clue in The Times
M
O
L
A
S
S
E
S
More clues leading to the result MOLASSES
- Syrup — huge number of lemmings initially stuck in it
- Bitter syrup produced by Missouri girls
- Second group of girls making treacle
- Idiot feeding burrowing animals syrup
- Sticky stuff trapping a vessel between piers
- Syrup: odd bits disappearing in bowl, a lot on the outside
- Spies eating idiot’s treacle
- Doctor gets the girls — that’s sweet
- After a short time, misses sweet stuff
- It’s sweet girl in some trouble
Buddy explains!

The straight part
We know that "Bitter syrup" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bitter syrup = molasses.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 MOLASSES mean?
MOLASSES noun- A thick brownish syrup produced in the refining of raw sugar.
- A shallow deposit of sandstone, shale and conglomerate in front of a rising mountain chain.