Hopefully one name will lead to arrest over heroin (9)

'hopefully one' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'name will lead to arrest over heroin' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'will' becomes 'ishall' (I am not sure about this - if you are sure you should believe this answer much more).
'lead to' says to take the initial letters.
'over' means one lot of letters goes inside another.
'heroin' becomes 'H' (H is a slang term for heroin).
The first letter of 'arrest' is 'a'.
'ishall'+'a'='ishalla'
'n' going within 'ishalla' is 'inshalla'.
'inshalla'+'h'='INSHALLAH'

Can you help me to learn more?