Expressed in numerals is this former drug (9)

I believe the answer is:

digitalis

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

'this former drug' is the definition.
'digitalis' can be an answer for 'drug' (I've seen this before). I'm not sure about the 'this former' bit.

'expressed in numerals is' is the wordplay.
'expressed in numerals' becomes 'digital' (I am not sure about this - if you are sure you should believe this answer much more).
'digital'+'is'='DIGITALIS'

Can you help me to learn more?

(Other definitions for digitalis that I've seen before include "Cardiac stimulant prepared from 11" , "Drug derived from foxglove leaves" , "plant making this drug?" , "Drug from foxgloves" , "medicinal drug" .)

I've seen this clue in the Sydney Morning Herald.

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.