The most common and most likely answer to this crossword clue is the 7 letter word CARDIAC
I've seen this crossword clue in Financial Times
C
A
R
D
I
A
C
More clues leading to the result CARDIAC
- Acid spattered under wheels of an organ
- Very ill person in short top and a cape
- Left off radical treatment caught affecting the heart
- Help artist up after Catholic’s first change of heart
- Eccentric in charge withholding ace of hearts
- Hearty greetings often the first clue
- Jack possibly needs one on account of his heart
- One ace — clubs — following, say, queen of hearts
- Perhaps automatic help given over first sign of crisis of the heart
- Joker gets one bill to do with heart
Buddy explains!

The straight part
We know that "of hearts" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case of hearts = cardiac.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CARDIAC mean?
CARDIAC noun- A person with heart disease.
- Heart disease.
- A medicine that excites action in the stomach.
- Pertaining to the heart.
- Pertaining to the cardia.
- Exciting action in the heart, through the medium of the stomach; cordial; stimulant.