Crossword Genius

Serious doctor with a reduced staff (7)

Ross

I believe the answer is:

drastic

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

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

'doctor with a reduced staff' is the wordplay.
'doctor with' becomes 'dr' (abbreviation. I am not sure about the 'with' bit.).
'reduced' means to remove the last letter.
'staff' becomes 'stick' (I've seen this before).
'stick' with its last letter taken away is 'stic'.
'dr'+'a'+'stic'='DRASTIC'

Can you help me to learn more?

(Other definitions for drastic that I've seen before include "'Severe, extreme (7)'" , "Severe and far-reaching" , "Radical, extreme" , "Having strong effect" , "Violent Doctor Crippen starts drinking wine" .)

I've seen this clue in The Times.
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