The most common and most likely answer to this crossword clue is the 8 letter word SEAMLESS
I've seen this crossword clue in The Daily Telegraph
S
E
A
M
L
E
S
S
More clues leading to the result SEAMLESS
- Immaculate – unlike coal mine?
- Main line during disorder is continuous
- Look down, coming across as smooth
- Main line in disarray? It’s flowing
- Black perhaps, medium and not as smooth
- Perfect — unlike a cricket ball?
- Perfect without stitches?
- . Appear smaller, say, and continuous
- Smooth ocean, deep water little inside
- Appear ‘lacking’, as one might say, without a stitch on
Buddy explains!

The straight part
We know that "flowing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flowing = seamless.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 SEAMLESS mean?
SEAMLESS adjective- Having no seams.
- Without interruption; coherent