Angel cuts up hearts (6)
I believe the answer is:
seraph
'angel' is the definition.
(seraph is a kind of angel)
'cuts up hearts' is the wordplay.
'cuts' becomes 'pares' (paring is a kind of cutting**).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'pares' written backwards gives 'serap'.
'serap'+'h'='SERAPH'
(Other definitions for seraph that I've seen before include "Angelic character" , "Leading angel" , "Angel with winged head of child" , "Angelic type" , "He raps the heavenly being wrongly" .)