The Wd means that he was wounded, and the 6/1343 is probably the reference of the casualty report notifying where and when he was wounded. Possibly his being wounded may be connected to him being awarded the Military Medal, which was gazetted 17.4.1917. Unfortunately most of the WW1 Casualty Reports have not survived and the best we have to go on are the newspaper reports which republished the War Office official listings. That said, a quick newspaper search has failed to bring up a report which includes him.
As he served on after 1920, his service record will have been retained by the MOD and is now in the process of being transferred and catalogued by TNA, and given his date of birth, it may shortly be digitised by Ancestry.