Can new basin be pot? (8)
'be pot?' is the definition.
(I've seen this before)
'can new basin' is the wordplay.
'new' is an anagram indicator.
'basin' is an anagram of 'nabis'.
(Other definitions for cannabis that I've seen before include "Soft drug", "Ban Incas from using this drug", "Grass", "Pot", "Most commonly used (mostly) illicit drug".)