Drug ring a girl goes after (10)
I believe the answer is:
belladonna
'drug' is the definition.
(I've seen this before)
'ring a girl goes after' is the wordplay.
'ring' becomes 'bell' (both can mean to call on the phone).
'girl' becomes 'donna' ().
'goes after' means one lot of letters go next to another.
'bell'+'a'+'donna'='BELLADONNA'
(Other definitions for belladonna that I've seen before include "Could it poison" , "drug supplier" , "Drug made from deadly nightshade" , "plant" , "Deadly nightshade or atropine" .)