Drugs an eccentric (8)
I believe the answer is:
crackpot
'an eccentric' is the definition.
(crackpot is a kind of eccentric)
'drugs' is the wordplay.
I cannot really see how this works, but
'drugs' could be 'pot' (slang term for mariujana) and 'pot' is found in the answer.
The remaining letters 'crack' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for crackpot that I've seen before include "Informal eccentric like damaged utensil" , "Nut" , "Ludicrous" , "Odd" , "Mad" .)