Hell on earth, son? Heroin and losing heart! (5)
I believe the answer is:
hades
'hell' is the definition.
('Hades' can be a synonym of 'hell')
'on earth son? heroin and losing heart' is the wordplay.
'on' means one lot of letters go next to another.
'earth' becomes 'e'.
'son?' becomes 's'.
'heroin' becomes 'h' ('H' can be a synonym of 'heroin').
'losing heart' means to remove the middle letters.
'and' with its middle taken out is 'ad'.
'e'+'s'='es'
'h'+'ad'='had'
'es' put after 'had' is 'HADES'.
(Other definitions for hades that I've seen before include "Infernal situation" , "gloomy place" , "It's classical hell in the shade" , "Mythological abode of the dead" , "Home of the souls of the dead" .)