Unadorned parts of wall are tiled over (7)
I believe the answer is:
literal
'unadorned parts' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'of wall are tiled over' is the wordplay.
'of' indicates a hidden word.
'over' is a reversal indicator.
'laretil' can be found hidden inside 'wall are tiled'.
'laretil' back-to-front is 'LITERAL'.
Can you help me to learn more?
(Other definitions for literal that I've seen before include "According to the letter" , "Taking words in their most basic sense" , "Unimaginative" , "Simple" , "typographical error" .)