Unknown leaves from freezer spiced up joint (6)
I believe the answer is:
reefer
'joint' is the definition.
('reefer' can be a synonym of 'joint')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for reefer that I've seen before include "Hand-rolled cigarette" , "Joint; spliff" , "A wool jacket; a spliff" , "roll of hemp" , "Smoking jacket and cigarette" .)