Current US prosecutor with influence not half in Western state (5)
I believe the answer is:
idaho
'half in western state' is the definition.
'idaho' can be an answer for 'state' (Idaho is an example). I'm not certain of the 'half in western' bit.
'current us prosecutor with influence not' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'us prosecutor' becomes 'da' (district attorney).
'with' says to put letters next to each other.
'influence not' becomes 'ho' (I can't explain this - if you can you should give a lot more credence to this answer).
'i'+'da'+'ho'='IDAHO'
Can you help me to learn more?
(Other definitions for idaho that I've seen before include "Another state" , "somewhere in the US" , "US state in the Rocky Mountains" , "One of 22 Across, capital Boise" , "Union member?" .)