Heart medicine is not analogue, for a start (9)
I believe the answer is:
digitalis
'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" .)