Today's heartless 'plays' (4)
I believe the answer is:
toys
'plays' is the definition.
(I've seen this before)
'today's heartless' is the wordplay.
'heartless' suggests removing the centre.
'todays' with its middle removed is 'TOYS'.
(Other definitions for toys that I've seen before include "Children's playthings" , "dolls, for example" , "Plays (with something), not seriously" , "Small dogs" , "Film" .)