Medal that's going heartless (4)
I believe the answer is:
gong
'medal' is the definition.
(informal term for a medal or prize)
'going heartless' is the wordplay.
'heartless' means to remove the middle letters.
'going' with its middle removed is 'GONG'.
'that's' is the link.
(Other definitions for gong that I've seen before include "Resonant metal disc" , "Dinner signal" , "Round plate that resounds when struck" , "Dinner call - medal" , "Dinner chime or slangy medal" .)