The most common and most likely answer to this crossword clue is the 7 letter word DENTIST
I've seen this crossword clue in The Daily Telegraph
D
E
N
T
I
S
T
More clues leading to the result DENTIST
- One filling small cavities over time?
- One fills some of the time at work
- Bash first for canine expert
- Professional looking down in the mouth?
- Extractor fan’s last in test I’d devised
- Cavity is treated initially by a health professional
- One with responsibility for bridge incident is testing spans
- Needing doctor? About time it’s inserted for Jock 7)
- He looks down in the mouth
- A number of people possibly sit and tend to shift about
Buddy explains!

The straight part
We know that "One able to fill some of the time at work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one able to fill some of the time at work = dentist.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 DENTIST mean?
DENTIST noun- A medical doctor who specializes in dentistry.