Mother’s in an outhouse, drunk (7)
I believe the answer is:
smashed
'drunk' is the definition.
(thesaurus)
'mother's in an outhouse' is the wordplay.
'mother's' becomes 'mas' (ma is a kind of mother).
'in' indicates putting letters inside.
'an outhouse' becomes 'shed' (I've seen this before).
'mas' placed into 'shed' is 'SMASHED'.
(Other definitions for smashed that I've seen before include "Vandalised" , "Affected by drug" , "bust?" , "Broke into small pieces" , "Broke; drunk (colloq.)" .)