This refers to Godwin’s step-daughter, Mary Wollstonecraft and Gilbert Imlay’s child, who was brought up in the belief that Godwin was her father. It is possible that the ‘explanation’ concerned the child's paternity. The entry is unusual in being underlined, which suggests it was a weighty matter. Fanny Imlay (generally known as 'Fanny Godwin') would then have been about 12.