Doctor not as healthy as dentist? (7)

I believe the answer is:

driller

I'm a little stuck... Click here to teach me more about this clue!

'dentist?' is the definition.
Both the answer and definition are singular nouns.
Maybe there's an association between them I don't understand?

'doctor not as healthy' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'not as healthy' becomes 'iller' (I've seen this in another clue).
'dr'+'iller'='DRILLER'

'as' is the link.

Can you help me to learn more?

(Another definition for driller that I've seen is " Borer".)

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.