Gets up and discards heated letters about heart disease (6)
I believe the answer is:
arises
'gets up' is the definition.
('arise' can be a synonym of 'get up')
'discards heated letters about heart disease' is the wordplay.
I cannot really see how this works, but
'letters' could be 'es' (more than one E) and 'es' is located in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is found within the answer.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for arises that I've seen before include "Gets out of bed" , "Gets up or comes up" , "Comes to notice, like committee business" .)