Literate means to read and write while illiterate means the opposite.
Accurate is the one that comes to mind.
There is no one-word 8-letter palindrome in English, apparently!
to simplify.
Cloister
An 8 letter word that means the inside of anything might be "interior." This word has 8 letters and would probably fit your crossword puzzle clue.
"Endorsement" is an 8-letter word that means official approval or support.
accurate
transfer
famished
Isolated
birthday
allocate
friction
memorize
Sensible.
Darkness.