The most common and most likely answer to this crossword clue is the 9 letter word DITHERING
I've seen this crossword clue in The Daily Telegraph
D
I
T
H
E
R
I
N
G
Buddy explains!

The straight part
We know that "Dubious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dubious = dithering.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 DITHERING mean?
DITHERING verb- To tremble, shake, or shiver with cold.
- To be uncertain or unable to make a decision about doing something.
- To do something nervously.
- To render an approximation of (an image, etc.) by using dot patterns to approximate (the features of) colors not in the system palette.
- To intentionally add noise to a signal to randomize errors.
- The act of one who dithers.