Shouldn't be drunk, so ought to be dismissed from some thoughts (5)
I believe the answer is:
meths
'shouldn't be drunk so ought to be dismissed from some thoughts' is the definition.
I can't tell whether this definition defines the answer.
'drunk so ought to be dismissed from some thoughts' is the wordplay.
'drunk so' becomes 'me' (I can't justify this - if you can you should believe this answer much more).
'to be dismissed from' is a deletion indicator.
'some thoughts' becomes 'thoughts'.
'thoughts' with 'ought' taken away is 'ths'.
'me'+'ths'='METHS'
Can you help me to learn more?
(Other definitions for meths that I've seen before include "unsuitable alcohol" , "Methylated spirits (colloq.)" , "Spirit" , "Fuel" , "Violet-coloured alcohol" .)