Stop heroin without husband's support (7)
I believe the answer is:
endorse
'support' is the definition.
(I know that support can be written as endorse)
'stop heroin without husband's' is the wordplay.
'stop' becomes 'end' (synonyms).
'heroin' becomes 'horse' (slang term for heroin).
'without' indicates named letters should be taken away.
'husband' becomes 'h'.
'horse' with 'h' taken out is 'orse'.
'end'+'orse'='ENDORSE'
(Other definitions for endorse that I've seen before include "Give one's approval to" , "Publicly approve" , "Give one's sanction to" , "Approve officially" , "Advocate" .)