Heart condition (6)
I believe the answer is:
angina
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">heart condition</span>' is the definition.<br/ ><span class="explanation-format__explanation">(angina is a kind of heart condition)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for angina that I've seen before include "medical condition" , "Severe chest pain" , "Pain from diseased heart" , "Sudden cardiac pain" , "heartfelt complaint?" .)