The most common and most likely answer to this crossword clue is the 4 plus 6 letter word SEMI LIQUID
I've seen this crossword clue in The Guardian
S
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Buddy explains!

The straight part
We know that "flowing only somewhat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flowing only somewhat = semi liquid.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 SEMI LIQUID mean?
SEMI LIQUID noun- Any substance with properties intermediate between those of a solid and a liquid.
- Having properties intermediate between those of a solid and a liquid.
- Somewhat liquid; able to flow or change, but not completely freely.