Small bags of top-class cocaine and heroin put in batches (7)
I believe the answer is:
sachets
'small bags' is the definition.
(a sachet is a small bag or container)
'top-class cocaine and heroin put in batches' is the wordplay.
I cannot quite understand how this works, but
'cocaine' could be 'c' (drugs abbreviation) and 'c' is found within the answer.
'heroin' could be 'h' (synonyms) and 'h' is located in the answer.
'top class' could be 'a' (top grade) and 'a' is present in the answer.
'put' could be 'set' (both can mean to place or position) and 'set' is present in the remaining letters.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
(Other definitions for sachets that I've seen before include "small bag" , "Bags" , "Small sealed packets, for cream or pot-pourri, say" .)