Lacking fluid, methinks you shouldn't drink it! (5)
I believe the answer is:
meths
'you shouldn't drink it' is the definition.
I can't judge whether this definition defines the answer.
'lacking fluid methinks' is the wordplay.
'lacking' suggests deleting specific letters.
'fluid' becomes 'ink' (ink is a kind of fluid).
'methinks' with 'ink' taken out is 'METHS'.
Can you help me to learn more?
(Other definitions for meths that I've seen before include "Methylated spirits (colloq.)" , "unsuitable alcohol" , "Violet-coloured alcohol" , "Spirit" , "Fuel" .)