Copper makes arrest linked to drug volume (6)
I believe the answer is:
cubage
'volume' is the definition.
(I've seen this in another clue)
'copper makes arrest linked to drug' is the wordplay.
'copper' becomes 'Cu' (Cu is the chemical symbol for copper).
'makes arrest' becomes 'bag' (I can't justify this - if you can you should give a lot more credence to this answer).
'linked to' says to put letters next to each other.
'drug' becomes 'e' (E is another name for ecstasy).
'cu'+'bag'+'e'='CUBAGE'
Can you help me to learn more?
(Other definitions for cubage that I've seen before include "Content" , "capacity" .)