Hazard, perhaps, of drug study (4)
I believe the answer is:
eden
'hazard perhaps' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'drug study' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'study' becomes 'den' (den can mean an office or study).
'e'+'den'='EDEN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for eden that I've seen before include "Anthony ---, PM 1955" , "Cornish garden; paradise" , "Former prime minister" , "at Number Ten once?" , "project in the south west" .)