Drug involves girl in basic changes (8)
I believe the answer is:
cannabis
'drug' is the definition.
(cannabis is a kind of drug)
'girl in basic changes' is the wordplay.
'girl' becomes 'ann' (woman's name).
'in' indicates putting letters inside.
'changes' indicates anagramming the letters.
'basic' with letters rearranged gives 'cabis'.
'ann' put into 'cabis' is 'CANNABIS'.
'involves' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for cannabis that I've seen before include "Soft drug" , "Hash" , "Ban Incas from using this drug" , "Hemp plant for making intoxicant drug" , "illegal drug supply" .)