A short drink, not a good one (5)
I believe the answer is:
meths
'a short drink not a good' is the definition.
I can't tell whether this definition defines the answer.
'one' is the wordplay.
I cannot really understand how this works, but
'one' could be 'me' (a setter might use 'one' to humourously mean 'me') and 'me' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for meths that I've seen before include "Fuel" , "unsuitable alcohol" , "Methylated spirits (colloq.)" , "Spirit" , "Violet-coloured alcohol" .)