Stone container with drug-free contents (7)
I believe the answer is:
peridot
'contents' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'stone container with drug-free' is the wordplay.
'stone container' becomes 'pot' (pot is a kind of container. I am not sure about the 'stone' bit.).
'with' means one lot of letters goes inside another.
'drug' becomes 'e' (E is another name for ecstasy).
'free' becomes 'rid' (similar in meaning).
'e'+'rid'='erid'
'pot' enclosing 'erid' is 'PERIDOT'.
(Other definitions for peridot that I've seen before include "olivine" , "A green semi-precious stone" , "mineral" , "I deport (anag) - gemstone" , "Top ride (anag) - gemstone" .)