Party animal, about 13, taking drugs (6)
I believe the answer is:
doping
'taking drugs' is the definition.
(doping is a kind of taking drugs)
'party animal about 13' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'animal about pn' becomes 'ping' (I can't explain this - if you can you should believe this answer much more).
'do'+'ping'='DOPING'
Can you help me to learn more?
(Other definitions for doping that I've seen before include "Taking 8" , "Giving sedative" .)