Simple, unadorned (5)
I believe the answer is:
plain
I believe this clue is a double definition.
'simple' is the first definition.
(similar in meaning)
'unadorned' is the second definition.
(associated in meaning)
(Other definitions for plain that I've seen before include "Unembellished" , "Evident; not fancy" , "lament" , "Not decorated" , "Unadorned; evident" .)