The bus decor becomes hidden (8)
I believe the answer is:
obscured
'hidden' is the definition.
(obscuring is a kind of hiding)
'the bus decor becomes' is the wordplay.
'becomes' indicates anagramming the letters.
'bus'+'decor'='busdecor'
'busdecor' anagrammed gives 'OBSCURED'.
(Other definitions for obscured that I've seen before include "unnoticed" , "Hid from view" , "Concealed from view, made indistinct" , "kept out of sight" , "Good news from clinic about schoolboy no longer" .)