Comedian insisting acts come primarily from the heart (7)
I believe the answer is:
cardiac
'the heart' is the definition.
(I've seen this before)
'comedian insisting acts come primarily' is the wordplay.
'comedian' becomes 'card' (card can mean a humorous person).
'primarily' says to take the initial letters.
The first letters of 'insisting acts come' is 'iac'.
'card'+'iac'='CARDIAC'
'from' is the link.
(Other definitions for cardiac that I've seen before include "Pertaining to the heart" , "one with a heart disorder" , "Relating to 8 down, part one" , "of hearts" , "Relating to the heart" .)