Gloomy music fan acquired heroin (4)
I believe the answer is:
goth
'gloomy music fan' is the definition.
(a fan of goth music)
'acquired heroin' is the wordplay.
'acquired' becomes 'got' ('get' can be a synonym of 'acquire').
'heroin' becomes 'h' (synonyms).
'got'+'h'='GOTH'
(Other definitions for goth that I've seen before include "One of Germanic tribe that invaded Roman empire" , "Rocker" , "One of an ancient Germanic nation" , "Rock music style" , "Rock music with gloomy lyrics" .)