Heart medicine is not analogue, for a start (9)

I believe the answer is:

digitalis

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'not analogue for a start' is the definition.
I can't judge whether this definition defines the answer.

'heart medicine is' is the wordplay.
'heart medicine' becomes 'digital' (I can't justify this - if you can 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 "Drug derived from foxglove leaves" , "Heart drug prepared from foxglove leaves" , "medicinal drug" , "Drug from foxgloves" , "Cardiac stimulant prepared from 11" .)

I've seen this clue in The Daily Express.

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