I've come across an obscure acrostic poem Carroll wrote for some friends in the 1860s, around the time he did "Alice." But no solution has survived. It's called "A Day in the Country" and is clever because it describes a day visiting the friends and photographing them, and the key words are PORTMANTEAU and PHOTOGRAPHY, both of which relate to the photography trip itself.

Some people have had a go at solving the clues, several of which are easier than others.
I can't reproduce the whole poem because I don't have permission, but I'm putting one verse here. The word can be of any length and it begins with A and ends with G. It describes the family getting ready to be photographed - this would have been done outside, in the 1860s.

"But is it really here you mean
To group the family together?
You really must devise a screen -
The sun will bake us brown as leather!" [A----G]