A blow to the heart would nauseate (3,3)
I believe the answer is:
put off
'nauseate' is the definition.
(thesaurus)
'a blow to the heart' is the wordplay.
'a blow' becomes 'puff' ('puff' can be a synonym of 'blow').
'the heart' indicates putting letters inside.
'puff' going around 'to' is 'PUT-OFF'.
'would' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for put off that I've seen before include "Don't encourage - delay" , "Defer to a later time, or alienate" , "confuse" , "Deter; deterred" , "Deter; delayed" .)