Loathsome husband developed fault importing drug (7)
I believe the answer is:
hateful
'loathsome' is the definition.
(I've seen this before)
'husband developed fault importing drug' is the wordplay.
'husband' becomes 'h' (abbreviation).
'developed' indicates anagramming the letters.
'importing' is an insertion indicator.
'drug' becomes 'e' (E is another name for ecstasy).
'fault' anagrammed gives 'atful'.
'atful' placed around 'e' is 'ateful'.
'h'+'ateful'='HATEFUL'
(Other definitions for hateful that I've seen before include "repellent" , "Abhorrent" , "Detestable" , "Unpleasant" , "Dreadful" .)