Internal
The word inside interviewing that means to bury is "inter".
inside
on means ontop where in can mean inside
The word into is a preposition. It means to go inside of.
An Anton is a word that means the inside of a molecule
aboard.
a term of driving inside a willa
The guys orions belt is inside the girls galaxy
In as inside would be naka.
Tmesis
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.
..Empty? Bare? Lacking?..