Not all stand by doctor, a radical (7)

I believe the answer is:

drastic

'radical' is the definition.
(drastic can mean radical or extreme)

I can't explain the remainder of the clue.

(Other definitions for drastic that I've seen before include "Grave" , "Severe and far-reaching" , "Having strong effect" , "Draconian" , "Extreme - violent" .)

I've seen this clue in The Times.

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