The most common and most likely answer to this crossword clue is the 6 letter word ORDURE
I've seen this crossword clue in The Guardian
O
R
D
U
R
E
Buddy explains!

The straight part
We know that "Dropping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dropping = ordure.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 ORDURE mean?
ORDURE noun- Dung, excrement.
- (by extension) Dirt, filth.
- (by extension) Something regarded as contaminating or perverting the morals; obscene material.