Aristocrat's sweet, giving drugs away (4)
I believe the answer is:
toff
'aristocrat's' is the definition.
(toff can mean an upper-class person)
'sweet giving drugs away' is the wordplay.
'sweet giving drugs' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'away' becomes 'off' (synonyms).
't'+'off'='TOFF'
Can you help me to learn more?
(Other definitions for toff that I've seen before include "Rich person (colloq.)" , "Nob" , "Posh bloke (sl)" , "A swell" , "Rich or upper-class person" .)