I would look into these records for Clara's husband Walter and son William.
Walter Herbert Harris's birth was registered Sep quarter 1885 in Merthyr Tydfil.
There is a Walter H Harris born abt 1885 death registered in Plymouth in Dec quarter 1952.
Herbert William G Harris's birth was registered in Sep quarter 1909 in Plymouth.
There is a Herbert W G Harris marriage to Lilian M Rowe registered in Devonport in 1934.
Lilian M Harris born abt 1915 died Sep quarter 1944 in Plymouth could be a match for Lilian M Rowe birth reg Dec quarter 1914 in Devonport.
There is then another Herbert W G Harris marriage in Plymouth in 1954 to Muriel B L M Thompson/Jarvis.
Muriel B L M Harris born abt 1913 died 1966 in Plymouth, a match for Muriel B L M Jarvis born Dec quarter 1913 in East Stonehouse.
Some names possibly to be getting on with.

If my guess as to a child of the Harris-Rowe marriage is correct, the child is living in Plymouth at present. I will PM you that info if you like JoGW, if you add one more post to the thread to make three.