With a will, the nation bans heroin (7)
I believe the answer is:
testate
'with a will' is the definition.
(I've seen this before)
'the nation bans heroin' is the wordplay.
I cannot really understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'nation' could be 'state' (synonyms) and 'state' is found within the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for testate that I've seen before include "Having made a legal will" , "Having left valid will at death" , "Having written a valid will" , "Having made a last will and testament" , "Having made a will before death" .)