Of the heart (7)

I believe the answer is:
cardiac
'of the heart' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cardiac that I've seen before include "Appertaining to the heart" , "Sort of surgery" , "Pertaining to the heart" , "Relating to the heart" , "Relating to 8 down, part one" .)