The most common and most likely answer to this crossword clue is the 7 letter word LEERIER
I've seen this crossword clue in The Daily Telegraph
L
E
E
R
I
E
R
More clues leading to the result LEERIER
Buddy explains!

The straight part
We know that "More dubious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more dubious = leerier.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 LEERIER mean?
LEERIER adjective- Cautious, suspicious, wary, hesitant, or nervous about something; having reservations or concerns.