The most common and most likely answer to this crossword clue is the 4 letter word SMUT
I've seen this crossword clue in Independent
S
M
U
T
More clues leading to the result SMUT
- . Obscene remarks from Greek character in street
- Obscene stuff saint found in Greek letter? On the contrary
- Some men use these tips for titillation
- Black stuff that could be blue
- Corporations rejected rude material
- Suggestive banter, perhaps, revealed in regressive corporations
- Repulsive material makes stomachs turn
- Obscene stuff turned stomachs
- Obscenity that turns stomachs
- Obscene material corporations rejected
Buddy explains!

The straight part
We know that "Obscene material" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case obscene material = smut.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 SMUT mean?
SMUT noun- Soot.
- A flake of ash or soot.
- Sexually vulgar material; something that is sexual in a dirty way; pornographic material.
- Obscene language; ribaldry; obscenity.
- Any of a range of fungi, mostly Ustilaginomycetes, that cause plant disease in grasses, including cereal crops; the disease so caused.
- Bad, soft coal containing earthy matter, found in the immediate locality of faults.
- To stain (or be stained) with soot or other dirt.
- To taint (grain, etc.) with the smut fungus.
- To become tainted by the smut fungus.
- To clear of the smut fungus.