Run heats of race-card (3,2,6)
I believe the answer is:
ace of hearts
'card' is the definition.
(ace of hearts is a kind of card)
'run heats of race' is the wordplay.
'run' is an anagram indicator (I've seen this in other clues).
'heats'+'of'+'race'='heatsofrace'
'heatsofrace' is an anagram of 'ACE OF HEARTS'.
(Other definitions for ace of hearts that I've seen before include "red card?" , "Scottish team's top player" .)