The most common and most likely answer to this crossword clue is the 9 letter word TOPSTITCH
I've seen this crossword clue in The Times
T
O
P
S
T
I
T
C
H
Buddy explains!
The straight part
We know that "Something from the sewer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something from the sewer = topstitch.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 TOPSTITCH mean?
TOPSTITCH noun- A sewing technique, most often used on garment edges such as necklines and hems, where it helps facings to stay in place and gives a crisp edge.
- An individual stitch of this kind.
- To stitch in this fashion.