Desire for sex, cocaine and heroin! (4)
I believe the answer is:
itch
'desire' is the definition.
(itch is a kind of desire)
'sex cocaine and heroin' is the wordplay.
'sex' becomes 'it' (a common euphemism).
'cocaine' becomes 'c' (drugs abbreviation).
'and' says to put letters next to each other.
'heroin' becomes 'h' ('H' can be a synonym of 'heroin').
'it'+'c'+'h'='ITCH'
'for' is the link.
(Other definitions for itch that I've seen before include "Hankering" , "It must be scratched" , "Restless longing" , "great desire" , "Seven-yearly desire" .)