The most common and most likely answer to this crossword clue is the 9 letter word OBSERVANT
I've seen this crossword clue in The Times
O
B
S
E
R
V
A
N
T
More clues leading to the result OBSERVANT
- Attentive valet supports old bachelor
- Inclined to notice former public schoolboy and valet?
- Likely to notice retainer having departed?
- Seeing nothing, first sign of blank page?
- With eyes open, he died needing help at home
- Devout old man embracing bishop
- Keen-eyed alumnus with man
- Attentive person in the employ of Eton alumnus?
- Dutiful man giving support to old bishop
- Sharp-eyed old maid, perhaps, smothers bachelor
Buddy explains!

The straight part
We know that "Dutiful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dutiful = observant.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 OBSERVANT mean?
OBSERVANT adjective- Alert and paying close attention; watchful.
- Diligently attentive in observing a law, custom, duty or principle; regardful; mindful.