Drunk back on hard stuff (4)
I believe the answer is:
Here is my best explanation:
'stuff' is the definition.
(both can mean nonsense)
'drunk back on hard' is the subsidiary indication.
'drunk' becomes 'sot' ('sot' can be a synonym of 'drunk').
'back' is a reversal indicator.
'on' means one lot of letters go next to another.
'hard' becomes 'h'.
'sot' written backwards gives 'tos'.
(Other definitions for tosh that I've seen before include "It's nonsense", "Intimate", "13 [TRIPE]", "Cobblers", "Humbug", "Nonsense (colloq.)", "garbage'", "Pal", "moonshine" and "Hooey".)