Where officials try to get through to public bar (7)
I believe the answer is:
prevent
'bar' is the definition.
(I know that bar is a more specific form of the action block)
I can't explain the rest of the clue.
(Other definitions for prevent that I've seen before include "Stop (an action)" , "Keep from arising" , "Stop, hinder" , "Thwart" , "Obviate" .)