Green’s Dictionary of Slang

grief n.2

[abbr. greefo n.]

(Aus. drugs) marijuana.

[US] (ref. to mid-1960s) B. Rodgers Queens’ Vernacular 210: marijuana [...] grief (kwn LV, mid ’60s tr Mex grifa = marijuana).
[Aus]Macquarie Dict. 🌐 grief noun a type of low-quality marijuana [rhyming slang for leaf].