Midshipman's joint (6)
I believe the answer is:
reefer
I believe this is a double definition.
'midshipman's' is the first definition.
(I've seen this before)
'joint' is the second definition.
(synonyms)
(Other definitions for reefer that I've seen before include "pot holder?" , "In slang, a marijuana cigarette" , "drugged cigarette" , "close-fitting garment" , "Midshipman (sl.)" .)