Engrave hearts and other things on top (4)
I believe the answer is:
etch
'engrave' is the definition.
(I know that engrave can be written as etch)
'hearts and other things on top' is the wordplay.
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'and other things' becomes 'etc' (abbreviation for et cetera).
'on top' means one lot of letters go next to another (in a down clue, some letters go above others).
'h' put after 'etc' is 'ETCH'.
(Other definitions for etch that I've seen before include "Cut lines with acid" , "Make carvings" , "Engrave deeply" , "Engrave metal plate using acid" , "Engrave; fix firmly" .)