3a) Barker is a bounder (8) ?P?I???R
8a) To carry on operations in a kind of shop (4) W?R? (WORK) ?
16d) Movable seat required for the biker (6) ?O?L?R
These are the three questions that give the three letters for 16a)
17a) View that offers little cheer to the prospector (5,7) BLEAK, OUTLOOK
20a) Records kept at the saw-mills? (3-5) LOG-ROLLS
22a) Cut off certain length of the port facilities (8) DOCKYARD