Bodily organ (5)
(Other definitions for heart that I've seen before include "Middle" , "Blood-pumping organ" , "show enthusiasm" , "one in suit" , "Crux" .)
'bodily organ' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for liver that I've seen before include "One extant" , "Vital organ" , "Bile-secreting organ" , "Part of body" , "Bile-secreting gland" .)