This man was enlisted as Walter Tydwell CLARKSON and so may be difficult for descendants to trace in the WW1 Service Records (WO 363):

Walter Tiddwell CLARKSOM, born Spalding Lincolnshire, August 1894.
Home: Kirton End.
Mother: Charlotte.
Enlisted February 1915, declared age 20y 185 days.
Served with the RFA (Regt No 93610) until de-mob in 1919

Anc****y, CLA, pages 193890 to 193902