Case after case of spice drug (8)
I believe the answer is:
sedative
'drug' is the definition.
(I know that sedative is a type of drug of abuse)
'case after case of spice' is the wordplay.
'case' becomes 'dative' (the dative case in grammar).
'after' says to put letters next to each other.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'spice' with its centre removed is 'se'.
'dative' after 'se' is 'SEDATIVE'.
(Other definitions for sedative that I've seen before include "Number" , "Sleeping drug" , "Deviates from calming medicine" , "Sleep-inducing drug" , "Calming drug" .)