The most common and most likely answer to this crossword clue is the 9 letter word DOUBTLESS
I've seen this crossword clue in The Daily Telegraph
D
O
U
B
T
L
E
S
S
More clues leading to the result DOUBTLESS
- Oldest bus around, certainly …
- Oldest bus in need of repair, of course
- Probably hypocritical to stock earliest of tomes on saints
- Certainly have fewer qualms
- Geminicarrying Taurus’s head to Scorpio’s
- Certainly not like Thomas
- Undeniably strange duets with awful slob
- Obviously cut down on workload but forced to come in
Buddy explains!

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 DOUBTLESS mean?
DOUBTLESS adjective- Characterized by or experiencing no doubt at all, certain; undoubted; undoubting.
- Free from fear or suspicion.
- Without doubt; very probably, in all likelihood; doubtlessly.