I don't think that Doris was ever married to the father of her child. At least, there is no sign of a likely marriage on the GRO index.
If Charles Bird/Clist is the father, and is also the man who married Edith Minnie Clist, he was not free to marry anybody until 1946, when Edith divorced him.
From The Somerset Herald 27 October 1945
Hemyock Wife Granted A Divorce
Mrs Edith Minnie Bird, of Fore-street, Hemyock, was granted a decree nisi by Mr Justice Wallington in the Divorce Court on Monday, on the ground of the misconduct of her husband, Mr Charles Bird. There was no defence.
The marriage of Mr and Mrs Bird took place in March 1910, and they afterwards lived at Hemyock. They have seven children. The petitioner's case was that her husband, who left her a number of years ago lived with a woman at Chiswick, London, in 1942 and 1943.
One of the Ancestry trees includes an image of the decree absolute, dated May 1946.
The 1942 marriage which some trees show was not to Doris.
All trees which show this man seem to agree that he was born Charles Bird, but ended his days as Harold Charles Clist in 1975, even though some trees approach him via the Clist family, and some via the family of his second marriage. This tends to suggest that the Bird/Clist change is known through family information.
Some of the trees include a photo of Charles in a uniform of some kind, which to my inexpert eye doesn't look like a naval uniform.