Pain yielding hearts — it’s a high card (3)
I believe the answer is:
ace
'a high card' is the definition.
(I've seen this before)
'pain yielding hearts' is the wordplay.
'pain' becomes 'ache' (ache is a kind of pain).
'yielding' indicates named letters should be taken away.
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'ache' with 'h' removed is 'ACE'.
'it's' is the link.
(Other definitions for ace that I've seen before include "Entertain" , "one among a set of diamonds" , "winner in court" , "hotshot" , "star" .)