I am stuck on a few Cryptic Crossword clues if anyone can help me:
8A - Impenetrable to the watcher or listener (6) (- - A - - - )
6D - Search oft pursued by knights of old (5) (- - - S - )
4D - A great long one runs in Yorkshire (4)
I have OUSE for this one - If correct, the U would be the first letter of 8A