Anger in heart of heiress (3)
I believe the answer is:
ire
'anger' is the definition.
(ire is intense rage)
'heart of heiress' is the wordplay.
'heart of' indicates a hidden word.
'IRE' can be found hidden inside 'heiress'.
'in' acts as a link.
(Other definitions for ire that I've seen before include "Hot temper" , "Displeasure" , "Paddy" , "heat" , "Anger, annoyance" .)